I thought it was caused by my GOTO main loop, so I tried replacing that with the default DO/LOOP main loop. But it's still happening.
I'm going to check this further the following days, see if it happens contantly, if it is all the sprite, if the game is still functional, if it is specific to the Android platform, etc.
But right now I just wanna ask if anyone have any clue what could be causing this?
When compiling for Android, I did set a checkmark at [v] Wake Lock ... no reason for this, I guess: When playing, the player moves his finger about constantly. But could [v] Wake Lock somehow be the reason for the disappearing sprites?