CSTMENU: multilevel custom menu with soft keys

[ramon_ea1gth]

Interesting. This means that WAIT(-1) is not working in your G1 by some reason and this causes the flicker, as the program is looping continuously through the non-working WAIT.
Is your G1 updated? What is the firmware version? You can see it with the Help button, Tree, About HP Prime.

[Edit]
One more question: despite the flicker, is CSTMENU (whatever version) giving the expected output when you press the softkey? If yes, this would mean that a touching event is being detected continuously, even when not touching the screen (thus flickering). If so, the reasons of the false touching event could be a software problem (firmware issue) or a hardware malfunction.