I’ve been using Firefox 97 for a few minutes and I’ve seen that warning about “Local storage error has occured, please refresh”. I don’t see any data loss yet though, nor are there errors in the console, just a warning (I’ll screencap it next time).
btw, I think occured is a typo: should be occurred
I came to my work computer this morning where I had a Firefox window open with Kinopio. The “Local storage error has occured” message was there. I hit refresh, and it was still there. At this point, I also saw the scarier error in the console about quota being exceeded.