Hello,
That sounds like an issue with the storage. Sometimes during Firefox update the storage gets broken and addon (or addons) needs to reinstalled. Make sure to restart Firefox after uninstalling (before installing it back).
Also, please visit this storage test page to see if the main database engine in your Firefox is working as it should:
https://firefox-storage-test.glitch.me/

Best regards,
Juraj Mäsiar