Shut down completely
Hold Power button for 20 seconds straight
Release
Wait 10 seconds
Power on normally
This resets the digitizer controller.
Test immediately after boot before opening other apps.
This fixes ghost input surprisingly often.
Open Device Manager → Human Interface Devices →
Disable HID-compliant touch screen
Restart.
Test drawing.
If the dots disappear → the Windows update broke palm rejection.
Uninstall the latest cumulative update installed right before this started.
Restart.
Test.
Shut down Surface completely.
Hold Volume Up → press Power → keep holding Volume Up until UEFI appears.
Use the Slim Pen 2 to:
Tap repeatedly
Lift slowly
Make quick movements
Hover close and lift
Watch for:
Random taps
Phantom selections
Screen reacting when you’re not touching
If it misfires here → likely hardware.
If it doesn’t → Windows/software issue.