Mine was doing that because the battery was exerting too much pressure on the board. I got one of the versions with 5
coils on the spring and I use 18650
batteries. With my battery in the unit the threads of the bottom cap sat roughly 1/8" above the body of the device, so I had to compress the spring quite a bit just to get the threads to engage and start screwing the cap on.
I pulled the spring out of the bottom cap, clipped off 2 of the
coils with a pair of side cutters, and stuck it back in (with the cut end pointed down so it won't mess up my batteries).
That resolved my screen problem instantly. Without screwing the cap down at all the threads can touch with the battery in place. When I do screw it down the battery is still held firmly in place, there's no rattling or anything, but now the top of my screen doesn't get pushed out of alignment. The screen now does its "look, I have power again" flash after turning the cap 1/2 to 1 full turn instead of flashing just from pushing the cap on hard enough to begin trying to screw it on.
If you're in the same situation that's where I'd recommend that you start. Your mileage may vary, proceed at your own risk, yadda yadda yadda. If you're going to do this start small, it's easy to cut off more but rather difficult make the spring grow longer.
There's supposed to be an "extended" cap that would achieve the same thing (reduce the pressure from sticking an 18650 battery in the ZMax), but if all you're using are 18650 batteries I don't see any reason to spend money on it.