PROBLEM: Imported video files seem to be off sync. This is observed through the waveform.
Here I am using video file source.mp4 in 23.976fps. Steps I have done:
1) import source.mp4 into Reaper.
2) export this as a WAV into source_through_reaper.wav
3) import both source.mp4 and source_through_reaper.wav into Premiere Pro and observe the difference. Time selection is one frame in length.
I expect Premiere Pro as a dedicated video editor to behave properly when importing video files.
EDIT: After further attempts to synchronise properly, I have found sometimes video files sound earlier and sometimes later.
Bellow in red is a wav file created in Premiere Pro from a video file. In blue is the same video file imported directly into Reaper. The difference here is around 60ms.