Recently my MBA started only letting me input in all caps such that I could not even sign in to my account. I connected a usb keyboard and it worked just fine so I thought I must have a hardware issue. Then I updated to the latest software (High Sierra) and the problem was fixed on my MacBook Air only to return again in a couple of days. So then I did a complete reset and the problem resolved only to return again in a couple of days. Now I don't know if it is a hardware or software issue or both! Any help would be greatly appreciated.