It looks like there is some case where the site can give back a 404 with html response, and the extension still tries to parse it as JSON. This causes Playnite to crash with an unrecoverable error. Log below.
22-05 12:58:57.209|INFO|SGDBMetadata:SGDB Initialized
22-05 12:58:57.209|INFO|SGDBMetadataProvider:AvailableFields
22-05 12:58:57.209|INFO|SGDBMetadataProvider:GetAvailableFields
22-05 12:58:57.209|INFO|SgdbServiceClient:getHeroImageUrl
22-05 12:58:57.209|INFO|SgdbServiceClient:
22-05 12:58:57.209|INFO|SgdbServiceClient:
22-05 12:58:57.209|INFO|SgdbServiceClient:
22-05 12:58:57.209|INFO|SgdbServiceClient:
22-05 12:58:57.209|INFO|SgdbServiceClient:
22-05 12:58:57.209|INFO|SgdbServiceClient:https://www.steamgriddb.com/api/v2/search/autocomplete/
22-05 12:58:57.469|INFO|SgdbServiceClient:<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<link rel="dns-prefetch" href="https://cdn2.steamgriddb.com/">
<link rel="preconnect" href="https://cdn2.steamgriddb.com/">
<link href="https://fonts.googleapis.com/css?family=Open+Sans:300,400,600,700&display=swap" rel="stylesheet">
<link rel="stylesheet" href="/static/assets/style.css?1620953414">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, shrink-to-fit=no, user-scalable=no">
<title>404 - Not Found - SteamGridDB</title>
<link rel="icon" type="image/png" href="/static/favicon/16.png" sizes="16x16">
<meta name="theme-color" content="#5fb4f0">
<meta property="og:url" content="https://www.steamgriddb.com">
<meta property="og:site_name" content="SteamGridDB">
<link rel="apple-touch-icon" href="/static/img/logo-512.png"/>
<link rel="preload" as="fetch" href="/api/public/user" crossorigin="anonymous">
<meta property="og:title" content="404 - Not Found">
<meta property="og:type" content="website">
<meta name="description" content="Download and share custom video game assets and personalize your gaming library.">
<meta property="og:description" content="Download and share custom video game assets and personalize your gaming library.">
<meta property="og:image" content="https://www.steamgriddb.com/static/img/logo-512.png">
<link rel="image_src" href="https://www.steamgriddb.com/static/img/logo-512.png">
<script async src="https://www.googletagmanager.com/gtag/js?id=UA-77667516-1"></script>
</head>
<body>
<div id="render-me-uwu" style="display:flex;flex-wrap:wrap;flex:1;width:100%;"></div>
<script src="/static/assets/3e96c4cb1561914eaf1b.js"></script>
<script>
window.dataLayer = window.dataLayer || [];
function gtag(){dataLayer.push(arguments);}
gtag('js', new Date());
gtag('config', 'UA-77667516-1');
</script>
<script defer src="https://static.cloudflareinsights.com/beacon.min.js" data-cf-beacon='{"rayId":"6537979b6fa7c90f","version":"2021.5.1","r":1,"token":"cc387f82b65b45c49d4817f6277638f9","si":10}'></script>
</body>
</html>
22-05 12:58:57.622|DEBUG|BaseCollectionView:Refreshing collection view filter.
22-05 12:58:57.742|ERROR|PlayniteApplication:Unhandled exception occured.System.AggregateException: One or more errors occurred. ---> Newtonsoft.Json.JsonReaderException: Unexpected character encountered while parsing value: <. Path '', line 0, position 0.
at Newtonsoft.Json.JsonTextReader.ParseValue()
at Newtonsoft.Json.JsonTextReader.Read()
at Newtonsoft.Json.JsonReader.ReadForType(JsonContract contract, Boolean hasConverter)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)
at Newtonsoft.Json.JsonConvert.DeserializeObject(String value, Type type, JsonSerializerSettings settings)
at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value, JsonSerializerSettings settings)
at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value)
at SGDBMetadata.SgdbServiceClient.Execute[T](RestRequest request) in U:\App_Dev\SGDBMetadata\SGDBMetadata\SGDBMetadata\SGDBService.cs:line 47
at SGDBMetadata.SgdbServiceClient.getSGDBGames(String searchName) in U:\App_Dev\SGDBMetadata\SGDBMetadata\SGDBMetadata\SGDBService.cs:line 56
at SGDBMetadata.SgdbServiceClient.getGameSGDBFuzzySearch(String gameTitle) in U:\App_Dev\SGDBMetadata\SGDBMetadata\SGDBMetadata\SGDBService.cs:line 125
at SGDBMetadata.SgdbServiceClient.getHeroImageUrl(String gameName, String platform, String gameId) in U:\App_Dev\SGDBMetadata\SGDBMetadata\SGDBMetadata\SGDBService.cs:line 241
at SGDBMetadata.SGDBMetadataProvider.GetBackgroundImage() in U:\App_Dev\SGDBMetadata\SGDBMetadata\SGDBMetadata\SGDBMetadataProvider.cs:line 135
at Playnite.Metadata.MetadataDownloader.ProcessField(Game game, MetadataFieldSettings fieldSettings, MetadataField gameField, Func`2 propertySelector, Dictionary`2 existingStoreData, Dictionary`2 existingPluginData) in G:\misc-source\Playnite\source\Playnite\Metadata\MetadataDownloader.cs:line 218
at Playnite.Metadata.MetadataDownloader.<>c__DisplayClass10_0.<DownloadMetadataAsync>b__0() in G:\misc-source\Playnite\source\Playnite\Metadata\MetadataDownloader.cs:line 494
at System.Threading.Tasks.Task.InnerInvoke()
at System.Threading.Tasks.Task.Execute()
--- End of inner exception stack trace ---
at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
at System.Threading.Tasks.Task.Wait(Int32 millisecondsTimeout, CancellationToken cancellationToken)
at System.Threading.Tasks.Task.Wait()
at Playnite.DesktopApp.ViewModels.DesktopAppViewModel.<>c__DisplayClass378_0.<UpdateLibrary>b__0() in G:\misc-source\Playnite\source\Playnite.DesktopApp\ViewModels\DesktopAppViewModel.cs:line 1230
at System.Threading.Tasks.Task.InnerInvoke()
at System.Threading.Tasks.Task.Execute()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
at Playnite.DesktopApp.ViewModels.DesktopAppViewModel.<UpdateLibrary>d__378.MoveNext() in G:\misc-source\Playnite\source\Playnite.DesktopApp\ViewModels\DesktopAppViewModel.cs:line 1241
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.AsyncMethodBuilderCore.<>c.<ThrowAsync>b__6_0(Object state)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
at System.Windows.Threading.DispatcherOperation.InvokeImpl()
at System.Windows.Threading.DispatcherOperation.InvokeInSecurityContext(Object state)
at MS.Internal.CulturePreservingExecutionContext.CallbackWrapper(Object obj)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at MS.Internal.CulturePreservingExecutionContext.Run(CulturePreservingExecutionContext executionContext, ContextCallback callback, Object state)
at System.Windows.Threading.DispatcherOperation.Invoke()
at System.Windows.Threading.Dispatcher.ProcessQueue()
at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
at System.Windows.Threading.Dispatcher.LegacyInvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs)
at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam)
at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg)
at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame)
at System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame)
at System.Windows.Application.RunDispatcher(Object ignore)
at System.Windows.Application.RunInternal(Window window)
at System.Windows.Application.Run(Window window)
at System.Windows.Application.Run()
at Playnite.PlayniteApplication.Run() in G:\misc-source\Playnite\source\Playnite\App\PlayniteApplication.cs:line 437
at Playnite.DesktopApp.ProgramEntry.Main(String[] args) in G:\misc-source\Playnite\source\Playnite.DesktopApp\ProgramEntry.cs:line 51
---> (Inner Exception #0) Newtonsoft.Json.JsonReaderException: Unexpected character encountered while parsing value: <. Path '', line 0, position 0.
at Newtonsoft.Json.JsonTextReader.ParseValue()
at Newtonsoft.Json.JsonTextReader.Read()
at Newtonsoft.Json.JsonReader.ReadForType(JsonContract contract, Boolean hasConverter)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)
at Newtonsoft.Json.JsonConvert.DeserializeObject(String value, Type type, JsonSerializerSettings settings)
at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value, JsonSerializerSettings settings)
at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value)
at SGDBMetadata.SgdbServiceClient.Execute[T](RestRequest request) in U:\App_Dev\SGDBMetadata\SGDBMetadata\SGDBMetadata\SGDBService.cs:line 47
at SGDBMetadata.SgdbServiceClient.getSGDBGames(String searchName) in U:\App_Dev\SGDBMetadata\SGDBMetadata\SGDBMetadata\SGDBService.cs:line 56
at SGDBMetadata.SgdbServiceClient.getGameSGDBFuzzySearch(String gameTitle) in U:\App_Dev\SGDBMetadata\SGDBMetadata\SGDBMetadata\SGDBService.cs:line 125
at SGDBMetadata.SgdbServiceClient.getHeroImageUrl(String gameName, String platform, String gameId) in U:\App_Dev\SGDBMetadata\SGDBMetadata\SGDBMetadata\SGDBService.cs:line 241
at SGDBMetadata.SGDBMetadataProvider.GetBackgroundImage() in U:\App_Dev\SGDBMetadata\SGDBMetadata\SGDBMetadata\SGDBMetadataProvider.cs:line 135
at Playnite.Metadata.MetadataDownloader.ProcessField(Game game, MetadataFieldSettings fieldSettings, MetadataField gameField, Func`2 propertySelector, Dictionary`2 existingStoreData, Dictionary`2 existingPluginData) in G:\misc-source\Playnite\source\Playnite\Metadata\MetadataDownloader.cs:line 218
at Playnite.Metadata.MetadataDownloader.<>c__DisplayClass10_0.<DownloadMetadataAsync>b__0() in G:\misc-source\Playnite\source\Playnite\Metadata\MetadataDownloader.cs:line 494
at System.Threading.Tasks.Task.InnerInvoke()
at System.Threading.Tasks.Task.Execute()<---
It looks like there is some case where the site can give back a 404 with html response, and the extension still tries to parse it as JSON. This causes Playnite to crash with an unrecoverable error. Log below.