[BUG] x264 doesn't encodes, even if the folder doesn't have special characters

[Selur]

Okay, problem is this:
FFMpeg requires the first frame to be 0001 not 0137.
Which is why I asked you to:

Try whether it helps to enable: Config->Internals->Avisynth->Alwayse use Avisynth

which should enforce Avisynth usage which like Vapoursynth allows to start at an arbitrary frame number.
-> So either follow that advice or rename your files or convince the ffmpeg developers that they should change the way they accept image sequence inputs.

Cu Selur