1.
Airports tell us their security x-rays 'are safe' for passengers' electronic devices. However some people report their devices did not work after being scanned.
2.
When a calculator misbehaves, some instructions recommend that you do a total reset by pressing a certain button at a certain time. Or by removing batteries for several minutes. Etc.
3.
In case the screen driver is at fault...
From what I read, the liquid crystals generally operate on an AC waveform, and a DC waveform at certain times. The AC portion must be centered around 0V, or else it shortens the crystals' life. (My information may be outdated.)
Since you state the screen remains lit, then it could be receiving a bad waveform. This is not easy to verify nor fix. Nevertheless a meter might reveal a bad voltage at some component.