I have the same anoying problem, since several months. On different computers, different systems (once Windows 7, 64-bit and once Windows 10, 64-bit), Opera always updatet to newest Version. Maybe, it has to do with my profile or some extensions?
Keyboard works well from starting Opera, but after a while not using it (and changing from different program-tabs) it stops reacting (nothing works, not even CTRL+...). Only thing then: to restart Opera. Mouse works fine all the time.
I would be glad if anyone knew how to stop this.