Chosen Solution
Recently this macbook started thinking ALT / Option key is always pressed and cant write properly, did try already SMC Reset, changing to new keyboard and just today swapping to “new” logic board from ebay and same.. its failling even from OSx Install terminal (takes some time to start failing like 5-10 mins) any idea why its failling?? (im out of ideas after new keyboard / logic board..)
Man I really hope you find the answer. Mine is doing the same thing except my shift key is the issue. It is incredibly annoying. What I have done to solve it is using Karabiner-Elements. It is an app that allows you disable specific keys, you could potentially just disable to ALT key in question and be golden. If you have replaced both the logic board and the keyboard, that’s impressive. Since the issue still exists after fixing those two parts, it could be that the flex cable between the keyboard and logic board is the issue. Did you replace this flex cable? If so, then I am relatively stumped. I am no computer wizard, but I suppose it could be an issue with the SDD somehow? I’ve read a few other threads on here with similar issues where people have suggested a virus causing their trackpad and keyboard issues.
