Quick update to everyone involved here:
I’ve been able to finally reproduce this issue with a consistent pattern. Within the same parent item, moving one child item up while removing another item that was before it will cause a desync of the list order. This was demonstrated in the video: Sorting/moving items doesn’t “sync” to different browser (?)
And now the good news: I have a confirmed fix for it! My patch will land in a few days to the webapp and in the next release cycle for desktop and mobile apps.
Once the fix has landed, I’ll be back to double-check with everyone that it’s indeed effective.
Thanks to everyone involved here and I sincerely apologize for not having this fixed earlier!