I’m guessing it has something to do with the encoding of the video (discussed here previously but without an actual solution Scroll Video buggy when scrolling up on Firefox - #8 by neofix).
Here is a long thread about optimizing videos for the library being used → Encoding video for the web · GitHub
It’s kinda involved so might wanna glance over it and maybe try re-exporting or converting using other tools if you don’t wanna fiddle too much with commands
There is an issue on github saying it’s janky on chrome which is just 4 days old → Video jerked in chrome · Issue #76 · dkaoster/scrolly-video · GitHub I’m guessing the poster will just be directed to the thread I linked above about encoding but who knows, maybe someone posts another solution there.
If you do get it figured out or get stuck using ffmpeg, feel free to post back 