DV50 mov files crash

[sophocles]

Deselecting 'Filtering->Vapoursynth->Misc->Source->Prefer LSMASHSource over LWLibAVSourcec for mp4/mov' works!

Is this a good option? I'm assuming LSMASHSource is usually better?

(I think that Windows Security is running its realtime protection, but I can't disable that.)

When I do the VapourSynth Preview with that option selected, I do get an error:

Failed to evaluate the script:
Python exception: lsmas: failed to get video track.

Traceback (most recent call last):
File "src\cython\vapoursynth.pyx", line 2832, in vapoursynth._vpy_evaluate
File "src\cython\vapoursynth.pyx", line 2833, in vapoursynth._vpy_evaluate
File "C:\Users\USER\AppData\Local\Temp\tempPreviewVapoursynthFile13_53_29_641.vpy", line 31, in
clip = core.lsmas.LibavSMASHSource(source="V:/Footage/Archival Footage/Capture/Press/TestFile.mov")
File "src\cython\vapoursynth.pyx", line 2580, in vapoursynth.Function.__call__
vapoursynth.Error: lsmas: failed to get video track.

Thanks much!