Try this.
BigSynth03.wav
signet.exe "bigsynth03.wav" add-loop 1461471smp --num-frames 1105396smp
Or:
signet.exe "bigsynth03.wav" add-loop 1461471 2566867
I tried many different ways but it just doesn't work at all for this sample (some others from this batch, too, but this one should hopefully help to uncover the issue). Why?
Loop points are indeed supposed to be 1461471-2566867. This is what RIFFView ends up showing:
