Sticky keys keep turning on automatically and left shift key not working

Hello,

My sticky keys keep turning on automatically every 5 minutes or so. I've disabled them in system preferences and the 'shift 5 times' function is off. I've restarted, shut down, researched articles, done everything I can find but the problem still persists.

I've also noticed at the same time my left shift button stopped working and think this might have something to do with it. I've followed the instructions in this post - ie. resetting the SMC and tried starting in safe mode but it didn't work for me. I couldn't even get starting up in safe mode working. I think because resetting the SMC and safe mode requires the left shift button to be functioning.

I'm on a MacBook Air (13-inch, Early 2015) running MacOS 10.14.3 - which I updated recently (maybe this has something to do with it?).

Thank you.