It's tedious but I'd do some basic troubleshooting like embargo all addons, not merely disable, and trash the user prefs. If you use sync with a Firefox account

It's tedious but I'd do some basic troubleshooting like embargo all addons, not merely disable, and trash the user prefs. If you use sync with a Firefox account, it'll have your history and bookmarks. Then add back add ons one at a time. I'm on 48.0.1 on Linux (on a Mac!) and I'm not having the problems you're describing.