I'm working in the browser, and am unable to save any activity that includes any applet. I'm able to save text just fine. I can add applets using the +ADD ELEMENT menu, and they appear to work fine, but when I hit SAVE or SAVE AND CLOSE, I always get the error message err_lost_backup. I've tried multiple browsers, private windows, and disabling any extensions. I've started the activity from scratch a number of times and tried multiple applets, and always get the same error. If I try to download the activity to my computer, I get only the saved part. I can't find any search results with this error. Any ideas?
I'm using a Mac with an M1 processor and MacOS 11.1.
I made a brief video showing the error: