So I too had this, my device since purchase always had the sensitivity issue where it would detect a scroll as a tap. America ATT model.
But I never had the random touch issue of it doing things on its own, ghost touches our button issues.
I was on dev preview, had my phone backed up, downgraded to 8 using the recovery tool, did not restore from backup, upgraded to Cyan, then hard reset the phone to restore my backup.
When I did this I started getting the ghost tapping, example, I have pin code lock screen, when I would wake the phone and attempt to put in my password it would always tap numbers multiple times. Also sometimes it would just start tapping numbers on its own.
The fix for the ghost and unintended multiple presses was to hit power button to sleep and the wake the device again with the power button. This would 90% fix the issue right away for me. But would come back shortly after. Also had camera launches without hitting the button.
Also another thing that seemed to fix beside asleep and wake, was hitting one of the capacitive buttons while on the lock screen right after it was woken up.
Turned out that under touch settings, turning off double tap to wake fixed my issue, I still very rarely get a scroll as a tap or keyboard doubles, but its very infrequent, before changing that setting it was happening all the time.
I think it has something to do with the restore of settings. I read somewhere that said the fix was to hard reset but do not restore from a backup, this sucks and I will not try it as I have too much stuff... But I will live without double tap to wake, its a shame cause on 8 and 8.1 DP I had no issues with this feature, while I did have sensitivity issues I did not have the ghost pressing.
Maybe try and turn that of or hard reset without a restore.