Not really sure what's going on here, but I've seen the "An error has occurred. Please restart Zotero." message quite a few times in the last couple of weeks.
Note that you're using a beta version. If that's not intentional, you should switch to the release version. (And if it is, be sure to mention that you're using the beta whenever reporting a problem.)
Did you submit that error report after the error occurred and before restarting Zotero?
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Did you submit that error report after the error occurred and before restarting Zotero?
I submitted the error report before restarting.