Same issue here (been happening intermittently for months if not years, actually) - been able to (somewhat) get around it by hitting the escape key, and retrying a few times ... sometimes that does the trick, sometimes it doesn't. Truly annoying.

The worse problem is that some of the other pop-ups (e.g., Conditional States) are far more consequential as 1) there's no work-around for them (for the issue described above one can go to the field manager and edit the field directly from there) and 2) while you think you're editing a restriction for one field, in the d/b it actually saves for another or for all fields that have restrictions applied to them ... simply put, it's become super unreliable. The way it manifests itself on Conditional States is you edit it for one field, but in the pop-up get the settings you know belong to another field (it's as if it was cached by the browser or something).

Wondering if there's browser or Joomla or server settings one can look into? Would be super grateful for any pointers. (Tried in multiple browsers and in both regular and incognito modes.)

Update: I played with a variety of use cases and the UX is such that the pop-up caches the previous pop-up content/UI. E.g., if I was editing a Conditional State for one field... then go to the field manager, and want to edit, e.g., an email field, click the "Editor" button to edit the message for the email field settings ... instead of the HTML editor I get the conditional state UI in the pop-up. I can reproduce this 100% now. On Seblod 3.22.1, Joomla 3.10.10.