[Postman]

Frame rate, yes. Codec, maybe. Movie length or file size, should not happen. Can you paste a Syncheck movie onto the video track in the middle of your session? Route beeps like all other session audio. Start playback well ahead of the point and solo the beeps track when you reach it for measurement. If sync has changed unexpectedly ahead of that point, you'll know.

In the bad old days and earlier versions of Pro Tools, QuickTime movies could slip sync and play remaining video out of sync until stopped and started again. I have even seen the same thing happen in Media Composer Video Satellite when playing certain files linked through AMA (which I believe is similar to how PT11's video engine works now). It shouldn't happen but it does.