Have you tried the keyboard test to check?
(hold COM button at boot, from boot menu select ‘test’ option). It will instruct you to test all the buttons and encoders so you know they’re good. You can quit the test mode anytime with the power switch.
first i would try to clean the button and the button contacts on the board
using compressed air and qtips and contact cleaner (like deoxit or similar)
most of the time if buttons are retriggering its because of a dirty contact or the rubber/silicone button
if that doesn’t work
next thing i would try is the ribbon cable connection. unseating and reseating the cable carefully.
i would also try a factory reset maybe before and/or after doing these things
maybe that might clear it up?
if that doesn’t work u could try replacing the keyboard board itself.
if that doesn’t work then u probably have some kind of dsp or main board issue or something more major
u could try replacing that board, or maybe at this point (or any point u don’t feel comfortable)
its time to contact TE