If others are having this issue, I deleted all forms of local storage (cookies, IndexDB, etc.) for the mail.google.com site, and that seems to have fixed the issue. It might be relevant that this happened after I upgraded Firefox.
YES
[flagged]
If others are having this issue, I deleted all forms of local storage (cookies, IndexDB, etc.) for the mail.google.com site, and that seems to have fixed the issue. It might be relevant that this happened after I upgraded Firefox.