I found the UI 0.18.0 | BE 0.18.1-rc.1 combination to be awfully slow and buggy.
Why not just update both Backend (BE) and Frontend (UI) to 0.18.0 and disable signups until 0.18.1 is released? I mean, lemmy.world really doesn't suffer from not having enough users, right?
0.18.0 would have given us the same issues we experienced today. We tried everyhing on a test-instance before but once the live was upgraded it went from good to bad very fast. Json errors, 2FA issues and then the slowness.
This is kinda odd since lemm.ml is running 0.18.0 on both BE and UI for quite a while now. Also I got the foillowing error message quite frequently and the UI was unresponsive until I refreshed the browser window. But maybe this was while UI 0.18.0 was active with BE 0.17.4. Looks like now eveyrthing is back to 0.17.4.
Update: Looks like deleting all lemmy.world site data in my browser (chrome) and logging in again solved this issue.