Looks like the virtual scroll works differently for the user profile feed (other feeds work fine though). Specifically, it doesn't preserve the hight of the feed item when it becomes hidden and because of that the height of the actual feed changes during scroll (even when no elements are added). Chromes manages to keep the scroll position fixed when the height change happens and so the jumping isn't visible to the user. However Safari (14) doesn't preserve the scroll position and therefore the scroll jumping occurs frequently for user profiles with lots of images. Will fix that.
Eugenijchanged title from Use fixed dimensions for media attachments to avoid layout jumping to Timeline with media attachments is jumping on load in Safari
changed title from Use fixed dimensions for media attachments to avoid layout jumping to Timeline with media attachments is jumping on load in Safari
Eugenijchanged title from Timeline with media attachments is jumping on load in Safari to User profile feed with media attachments is jumping on load in Safari
changed title from Timeline with media attachments is jumping on load in Safari to User profile feed with media attachments is jumping on load in Safari