On my brother's MacBook Pro, suddenly the Enter, right shift, and right alt keys do not work properly anymore. It works with an external keyboard, though. PRAM/SMC reset did not help. Strangely, at least the shift and alt keys seem to at least work mechanically: When I press shift and a key, both inputs are completely ignored. When I press e.g. shift/alt/a, the correct special character is printed. So at least shift/alt seem to work, but only in some circumstances.
Any ideas on how to solve this?