Yes. Plenty. Firefox seems to have problems releasing memory in off screen DOM objects resulting in an endless memory leak. It also has a tendency to fully lock up the UI when a web page displays more than 3 pre-loaded video elements at once - a problem that is resolved by minimising and restoring the window using windows hotkeys. All in all you can't do something as mind boggling complex as scrolling through reddit without hitting some breaking bug.
It has a problem with cache release meaning your cache will grow endlessly and fill up the disk space if you're using an webapp and don't close the tab.
That's just the bugs I come across. Then there's their distain for users. Who can forget a few years ago re naming the menu item "Copy Link Loc(A)tion" to "Copy (L)ink" because apparently one was too confusing for user. Apparently they have no problem fucking with their entire user's base's 20 years of developed muscle memory while also extending a middle finger to right handed people who used to not need to take their hand off their mouse to use a commonly used keyboard shortcut.
Oh but there's no "a" in "Copy Link" they said as a justification. When I pointed out that "Preview Link" doesn't have a J in it, "Split view" doesn't have an M in it, and "Inspect" doesn't have a Q in it, they quickly locked the thread.
Bonus points: There was a plugin that restored the broken functionality, but it was from an unvetted Chinese developer and hurrah now all the users who liked their muscle memory ended up with malware.
Sorry but if they tell their users they can go fuck themselves, then they deserve the same reaction from their users. I still try to like Firefox, I still have it installed and see every so often if it is actually usable or not, but god fucking damnit this is a toxic relationship.