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.