I was in my type 87 Japanese ‘Gepard like’ tank and I was scanning around with my binoculars. When I spotted a plane coming in I immediately switched radar mode without leaving binoculars, I just hit the keybind to go right into radar mode. This prevented me from firing the main weapon while in the radar mode screen. I had to exit radar mode which put me right back into binoculars then exit that to be able to fire my main gun again.
Not necessarily a bug, but perhaps and unintended issue?
