Weird intermittent keymapping issue on Windows

I've got the strangest issue lately. Multiple times a day, one key is duplicating another i.e. a short while ago pressing L was producing E (as well as E still producing E). I get the same behaviour when using my bluetooth mechanical keyboard (using ZMK firmwars) as well as on my built-in laptop keyboard which makes me think it's a Windows driver issue. I am on Microsoft Windows 10 Pro (Version 10.0.19045 Build 19045) on an HP EliteBook 830 G5. The first time I noticed it, it was producing really weird symbols but I eventually figured out that I had accidentally activated a Dyalog APL keyboard

Question by snth on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.