Good to hear, i downgraded with no problems.
FYI i only have the classic editor and the same problem though – so Gutenberg is not the culprit afaik as it has never been installed (WP 4.9.8).
Having this issue too.
5.7.7 is completely unusable for now – as backend looks like a disaster zone.
What is the status on fixing this?
Also how can such a crazy error make it into a release?
( ps. i feel for you guys – dev’ing is hard these days 🙂 )