MacBook Air Keyboard freezes intermittently, including USB keyboard. Trackpad/mouse fine. Help?

My MacBook Air (early 2014) has developed an issue in the last few months where the keyboard freezes and will not unstick. Weirdly, it doesn't seem to be specifically a hardware issue. I ran a diagnostic thing on the laptop itself yesterday and it found no issues. Plus, the external keyboard plugged in via USB also simultaneously becomes unresponsive.

Unlike other users with keyboard issues, my trackpad (and external mouse) remain responsive so I am able to put the mac to sleep or try to close out windows this way but nothing seems to help short of restarting the whole thing with a reset of the keyboard (hitting some combination of option keys I found online, so at least it can register that even while it refuses to type).

Often (always?) when this happens I notice the caps lock light is stuck on even though I never use caps lock.

Does anyone know how to fix this? It is extremely inconvenient and keeps interrupting me in the middle of writing, grading, etc. I found maybe one post that seemed close to my issue, but the link is shares to some 'solutions' is now broken: https://discussions.apple.com/thread/3040536