I may have found an issue with the Atari 5200 version of the game. We played it on Friday on the ZeroPage Homebrew stream and after approx 9 minutes the screensaver kicked in and none of the buttons on the joystick were able to disable it.
Here's a link to just before the screensaver kicked in on the ZPH stream.
Excellent game and super fun but it switched to hard mode when the screensaver goes on!