When i first start firefox idk what really causes it and can't really reproduce the issue and it's random on all pc's/os's i try by one thing in common is that it happens when i use my synced firefox account So when it starts and i open a website it "sometimes" just closes immediately and have to reopen that website Also happens from a saved session. It's the wierdest issue i have ever seen as it's random and there isn't a way to really reproduce it to as far as i know. I am sure it's some setting that is synced with my account as i didn't have the problem before i have had this issue for a few years now i think and it's really annoying and have looked if there was anything similar to this issue and couldn't find anything.