Hi Chaps. Old thread I know but wondering if you guys got to the bottom of this?
I am running Pi 3 with retropie 4.3 on a 1080p HDTV and lr-mame2003.
Output resolution is set to 1080p/60 and when render resolution is also set to 1080p the bezels work perfectly (with some performance issues).
When my render resolution is set to 800x600 I have the same issues as OP.
Running the render res at 800x600 gives me super smooth scrolling whereas with 1920x1080 i get snatchy/glitchy scrolling.
Happy to provide more info, just wondered if there was something obvious that I am missing.
Great work Floob! Cheers