Thanks Alex.
I checked about 10 DVDs, all ripped to VOBs (over a 3 year period by DVDFab).
I tried several things:
Chapters: skip forward or back worked consistantly for me.
FF worked @ 5x, Rew mostly worked @ 5x, but if I started Rew right at a chapter, it looked like it skipped to the beginning of the previous chapter.
Fast forward (5x) shows smooth speeded up video motion without sound. Rew (5x) shows frozen video while the time index skips backward at ≈ 60 sec intervals. The movie starts instantly when play is pressed without any vid/aud sync issues.
FF @ 20x would always hang, Rev @ 20x actually worked a time or two, but usually hangs.
My time skips are set to 1:00 min forward & 15 sec backward.
When I do a single skip forward the video goes forward to what looks like the proper point and stops, there are no sounds or noises.
Waiting doesn't help, but if I pause it, then press play, the video will start and about a second later, the sound starts & they are in sync.
Also, if I drag the position indicator at the top of the screen to a new location, I get exactly the same behavoir as skip forward/backward.
The behaviors described above happened with every VOB file I played.
All of the above functions are working as they should when Mpeg 2 and .ts files are played (both recorded HDTV and ripped blurays).