> I also seem to have an annoying bug in mobile where after a while long tap on link no longer opens the contextual menu.

I encountered a bug matching this description on my S7. So far I discovered that it's correlated to the number of tabs open; around 70 tabs, the context menu appears after perceptible delay, which increases with the number of open tabs. I think I reached something around 90 tabs before I couldn't long-tap on links any more. Closing tabs makes the problem go away.

I'd say "go ahead and report it", but I too have uBlock installed, so I can't say if it's unrelated. uBlock was the very reason I switched to Firefox on Android anyway.