diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4eb37ef..14c169d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,13 +1,10 @@
 cmake_minimum_required(VERSION 3.25)
 set(CMAKE_OSX_DEPLOYMENT_TARGET "13.3" CACHE STRING "needs at least 13.3")
-project(QtPMbrowser VERSION 2.5.0 LANGUAGES CXX)
-set(MY_RELEASE_DAY "2026-03-13")
-set(MY_COPYRIGHT "2020 - 2025 Christian R. Halaszovich")
+project(QtPMbrowser VERSION 2.5.1 LANGUAGES CXX)
+set(MY_RELEASE_DAY "2026-05-4")
+set(MY_COPYRIGHT "2020 - 2026 Christian R. Halaszovich")
 set(LINUX_RELEASE_DESCRIPTION "
-    <p>improved feature: show stimulus protocols in table view</p>
-    <p>improved feature: 'Select Parameters Dialog' allows selecting / de-selecting all options of a section</p>
-    <p>improved feature: show amplifier state in table view</p>
-    <p>bugfix: handle unicode in filenames (for loading and exporting)</p>
+    <p>new feature: support unbundled PM files</p>
 ")
 
 set(CMAKE_CXX_STANDARD 20)
diff --git a/QtPMbrowser/linux_deploy/de.halaszovich.pmbrowser.desktop.in b/QtPMbrowser/linux_deploy/de.halaszovich.pmbrowser.desktop.in
index 26cbe24..0da8bad 100644
--- a/QtPMbrowser/linux_deploy/de.halaszovich.pmbrowser.desktop.in
+++ b/QtPMbrowser/linux_deploy/de.halaszovich.pmbrowser.desktop.in
@@ -5,6 +5,5 @@ Name=PM browser
 Comment=Browse PM dat files
 Terminal=false
 Categories=Science
-Exec=QtPMbrowser %u
-#MimeType=application/octet-stream
+Exec=QtPMbrowser %f
 Icon=${MY_APP_ID}
diff --git a/QtPMbrowser/pmbrowserwindow.cpp b/QtPMbrowser/pmbrowserwindow.cpp
index 04f3fde..7cff4b5 100644
--- a/QtPMbrowser/pmbrowserwindow.cpp
+++ b/QtPMbrowser/pmbrowserwindow.cpp
@@ -1,5 +1,5 @@
 /*
-    Copyright 2020 - 2025 Christian R. Halaszovich
+    Copyright 2020 - 2026 Christian R. Halaszovich
 
      This file is part of PMbrowser.
 
@@ -172,7 +172,9 @@ void PMbrowserWindow::animateTraceList(const QString& info_text, const std::vect
         if (progress.wasCanceled()) {
             break;
         }
-        ui->renderArea->renderTrace(trace_list.at(i), infile);
+        if(!ui->renderArea->renderTrace(trace_list.at(i), infile)) {
+            break;
+        }
         ui->renderArea->repaint();
 #ifdef __APPLE__
         // unfortunately, on macOS Qt doesn't support QWdiget::repaint
@@ -303,18 +305,25 @@ void PMbrowserWindow::loadFile(QString filename)
     QSettings settings;
     settings.setValue("pmbrowserwindow/lastloadpath", lastloadpath);
     datfile = std::make_unique<DatFile>();
+    bool do_retry = false;
     try {
         datfile->InitFromStream(infile);
     }
+    catch (const hkLib::fileformat_error& e) {
+        datfile = nullptr;
+        infile.seekg(0, std::ios_base::beg);
+        qDebug() << e.what();
+        do_retry = true;
+    }
     catch (const std::exception& e) {
-        //QMessageBox::warning(this, QString("File Error"), 
-        //    QString("error while processing dat file:\n") + QString(e.what()));
+        QMessageBox::warning(this, QString("File Error"), 
+            QString("error while processing dat file:\n") + QString(e.what()));
 		qDebug() << e.what();
         datfile = nullptr;
-        infile.seekg(0, std::ios_base::beg);
-        //infile.close();
+        //infile.seekg(0, std::ios_base::beg);
+        infile.close();
     }
-    if (!datfile) {
+    if (do_retry && !datfile) {
         try {
             // we might habe an unbundled dat file
             datfile = std::make_unique<DatFile>();
diff --git a/QtPMbrowser/pmbrowserwindow.h b/QtPMbrowser/pmbrowserwindow.h
index 7b2ad70..0198286 100644
--- a/QtPMbrowser/pmbrowserwindow.h
+++ b/QtPMbrowser/pmbrowserwindow.h
@@ -1,5 +1,5 @@
 /*
-    Copyright 2020 - 2023 Christian R. Halaszovich
+    Copyright 2020 - 2026 Christian R. Halaszovich
 
      This file is part of PMbrowser.
 
diff --git a/QtPMbrowser/renderarea.cpp b/QtPMbrowser/renderarea.cpp
index f6e6dc3..0532629 100644
--- a/QtPMbrowser/renderarea.cpp
+++ b/QtPMbrowser/renderarea.cpp
@@ -713,7 +713,7 @@ void RenderArea::zoomIn(double x_center, double y_center, double factor)
     update();
 }
 
-void RenderArea::renderTrace(const hkLib::hkTreeNode* TrRecord, std::istream& infile)
+bool RenderArea::renderTrace(const hkLib::hkTreeNode* TrRecord, std::istream& infile)
 {
     using namespace hkLib;
     char dataformat = TrRecord->getChar(TrDataFormat);
@@ -736,7 +736,7 @@ void RenderArea::renderTrace(const hkLib::hkTreeNode* TrRecord, std::istream& in
 		}
 		else {
 			QMessageBox::warning(this, QString("Data Format Error"), QString("Unknown Dataformat"));
-			return;
+			return false;
 		}
         
         addTrace(DisplayTrace(
@@ -751,12 +751,13 @@ void RenderArea::renderTrace(const hkLib::hkTreeNode* TrRecord, std::istream& in
 	catch (const std::exception& e) {
 //        newYtrace.data.clear();
 		QMessageBox::warning(nullptr, "File Error", e.what());
-		return;
+		return false;
 	}
 
     if (do_autoscale_on_load) { autoScale(); }
     else { update(); } // update is usually done within autoScale()
     setMouseTracking(true);
+    return true; // success
     }
 
 void RenderArea::addTrace(DisplayTrace&& dt)
diff --git a/QtPMbrowser/renderarea.h b/QtPMbrowser/renderarea.h
index 68c5032..279643d 100644
--- a/QtPMbrowser/renderarea.h
+++ b/QtPMbrowser/renderarea.h
@@ -48,7 +48,7 @@ class RenderArea : public QWidget
     explicit RenderArea(QWidget *parent = nullptr);
     ~RenderArea();
     bool noData() { return !yTrace.isValid(); };
-    void renderTrace(const hkLib::hkTreeNode* trace, std::istream& infile);
+    bool renderTrace(const hkLib::hkTreeNode* trace, std::istream& infile);
     void addTrace(DisplayTrace&& dt);
 
     /// <summary>
diff --git a/doc/index.rst b/doc/index.rst
index 7571b4c..94cb055 100644
--- a/doc/index.rst
+++ b/doc/index.rst
@@ -15,8 +15,8 @@ Welcome to PMbrowser's documentation!
 
 :program:`PMbrowser` is open-source software aimed at electrophysiologists who use :program:`PATCHMASTER` or
 :program:`PATCHMASTER NEXT` from `HEKA <http://www.heka.com/downloads/downloads_main.html#down_patchmaster_next>`_ and
-:program:`IgorPro` of `WaveMetrics <https://www.wavemetrics.com/>`_. It can open bundled data files (:file:`.dat`) and 
-export :program:`IgorPro` compatible files (and supports some additional export formats,
+:program:`IgorPro` of `WaveMetrics <https://www.wavemetrics.com/>`_. It can open data files (:file:`.dat`) and 
+export :program:`IgorPro` compatible files (and supports some additional export formats, e.g. :program:`numpy`,
 see :ref:`intro-label` for details).
 
 But even if you do not use :program:`IgorPro`, you might find :program:`PMbrowser` useful for browsing PatchMaster files
diff --git a/doc/introduction.rst b/doc/introduction.rst
index 0269126..44c3999 100644
--- a/doc/introduction.rst
+++ b/doc/introduction.rst
@@ -3,7 +3,7 @@
 What can :program:`PMbrowser` do for you?
 -----------------------------------------
 
-It can open bundled data files (:file:`.dat`) created by :program:`PATCHMASTER` or
+It can open data (bundled and unbundled) files (:file:`.dat`) created by :program:`PATCHMASTER` or
 :program:`PATCHMASTER NEXT`.
 
 It has been tested with files created by versions of :program:`PATCHMASTER`
@@ -50,4 +50,4 @@ You can use it freely. The source code can be found `here <https://github.com/Ch
  variant under active developement by HEKA, cannot read data files created by old versions of :program:`PATCHMASTER`.
  One intention for the creation of :program:`PMbrowser` was to provide support for reading these old data files for
  users who now use :program:`PATCHMASTER NEXT`.
- 
\ No newline at end of file
+ 
diff --git a/hekatoolslib/DatFile.cpp b/hekatoolslib/DatFile.cpp
index f389f78..258a725 100644
--- a/hekatoolslib/DatFile.cpp
+++ b/hekatoolslib/DatFile.cpp
@@ -49,10 +49,10 @@ void DatFile::InitFromStream(std::istream& infile)
     if (!isValid) {
         bool isInvalidBundle = std::memcmp(bh->Signature, BundleSignatureInvalid, 8) == 0;
         if (isInvalidBundle) {
-            throw std::runtime_error("invalid bundle signature");
+            throw fileformat_error("invalid bundle signature");
         }
         else {
-            throw std::runtime_error("invalid file (not a PM dat file)");
+            throw fileformat_error("invalid file (not a PM dat file)");
         }
     }
 
diff --git a/hekatoolslib/DatFile.h b/hekatoolslib/DatFile.h
index 62c34cd..a35eaf9 100644
--- a/hekatoolslib/DatFile.h
+++ b/hekatoolslib/DatFile.h
@@ -3,7 +3,7 @@
  */
 
 /*
-	Copyright 2020 - 2023 Christian R. Halaszovich
+	Copyright 2020 - 2026 Christian R. Halaszovich
 
 	 This file is part of PMbrowser.
 
@@ -33,11 +33,17 @@
 #include <algorithm>
 #include <type_traits>
 #include <cassert>
+#include <stdexcept>
 #include "machineinfo.h"
 #include "hkTree.h"
 #include "helpers.h"
 
 namespace hkLib {
+	/// @brief thrown if file is not a bundled dat file
+	class fileformat_error : public std::runtime_error {
+	public:
+		fileformat_error(const std::string& msg) : std::runtime_error(msg) {}
+	};
 
 	/// <summary>
 	/// each BundleItem describes offset and length of
diff --git a/hekatoolslib/hkTree.cpp b/hekatoolslib/hkTree.cpp
index cd1eb47..13b0589 100644
--- a/hekatoolslib/hkTree.cpp
+++ b/hekatoolslib/hkTree.cpp
@@ -1,5 +1,5 @@
 /*
-	Copyright 2020 - 2022 Christian R. Halaszovich
+	Copyright 2020 - 2026 Christian R. Halaszovich
 
 	 This file is part of PMbrowser.
 
diff --git a/hekatoolslib/hkTree.h b/hekatoolslib/hkTree.h
index bad24cc..fba8d45 100644
--- a/hekatoolslib/hkTree.h
+++ b/hekatoolslib/hkTree.h
@@ -1,5 +1,5 @@
 /*
-    Copyright 2020 - 2022 Christian R. Halaszovich
+    Copyright 2020 - 2026 Christian R. Halaszovich
 
      This file is part of PMbrowser.