There just seems to be no rhyme or reason to the errors (although the same error occurs consistently on certain frames).
I thought it might be something to do with drop frame, variable frame rates, the clip being different from the sequence, or other oddities, but the error occurs at simple constant frame rates like 25 fps. I feel like I’ve tried everything to discover what the pattern is, but it seems entirely random. …about 50% of the time the I/O points (in the source window) are set with a 1 frame error (sometimes 2 frames out).
I’ve run into a frustrating brick wall when using: tInPoint(seconds)