If Android touch screen detects presses wrongly, try freeing space (memory).

For a few weeks my Android phone's screen has responded wrongly to my presses on the virtual keyboard. When  I press A, a different thing appears. I first thought it was due to screen scratches but now I doubt it.

Yesterday I freed memory by uninstalling Messenger app, and had about 140 megabytes of free space.

Then the problem seemed to disappear, though a few times today the phone has not correctly shown what  I press.

As an aside : if your screen is wet, it will wrongly detect touches. But that is not the problem  I'm talking about.