Which version are you using and are you fully updated?
I have four machines running the latrest version of FF 64, two on Win 7 and two with Linux Mint 19.1 (Tessa). I seem to be good.
My main problem with FF was having Outlook.live.com not liking to send or reply to messages, which I learned is an occasional glitch based on a bad update/upgrade.
Try starting FF in safe mode or without add-ons (refresh) and rebuild one add-on at a time.
__________________
I don't know nothing, and I memorized it in school and got this here paper I'm proud of to show it.