If Firefox was stopped forcibly for a few times then add-ons disappear from Firefox menu and stop working. But if I try to disable and re-enable add-on this issue no longer reproducable. How to reproduce: 1. Open Firefox 2. Go to Settings->Apps->Firefox 3. Force stop Firefox 4. Repeat steps 1 - 3 5. After these steps add-ons disappear from Firefox menu. Any other way to fix this or prevent this from happening?