Hello everyone!
I've bought a used Pixel Tablet some time ago that had the commonly known ghost-touch issue. I installed GrapheneOS and activated the alternative touchscreen-mode to avoid ghost-touches in the display settings.
After that everything worked perfectly fine.
After some time of usage I wanted to demonstrate to someone what the ghost-touches looked like. Therefore, I disabled named setting again. To my suprise: there weren't any ghost touches anymore, everything worked flawlessly. My guess was that the setting must have reset something in the screen calibration that permanentely fixed the problem.
Later that day I noticed that the tablet wouldn't react to my touches sometimes. It didn't bother me a lot since it would instantley disappear when I turned the device off and on again (just stand-by, not a restart).
The next day, the problem had worsened. The touchscreen was suddenly reacting very poorly to any input, to the point where the device wasnt usable. I thought it was some kind of bug and unfortunately didn't draw any connection to the setting I changed previously. Therefore, I force-restarted the device. After that, the touchscreen stopped working entirely. No reaction whatsoever to any swiping or tapping. The buttons seem to work without any issues. The device isn't frozen, it just doesnt recognize any touches.
I then tried to connect a keyboard and a mouse via USB, but no cursor appeard/I couldn't type. I tried it on my Pixel 6 (also runs GrapheneOS), and the cursor would only appear once I navigated to the mouse setting. I can't do that on the tablet, as I'm stuck on the lockscreen.
I also sideloaded the newest stable OTA release for my device, but it didn't bring any success.
Since someone with a similar issue mentioned charging the device would temporarily resolve the problem, I also tried that, but it didn't work either.
It could also be that it is an hardware issue (especially since the tablet had ghost-touches from the beginning), but the fact that it coincides with the setting-change makes me doubt it. Also note: when you enable the setting for the alternative touchscreen mode, you have to confirm the change within a few seconds or it gets reseted to default - in case the touchscreen doesn't work after the change.
I haven't tried factory resetting the device yet, since I would like to keep the stored data - if possible. Maybe someone here has another idea what I could try.
Best regards :)