Just wanted to do a quick IT support post since this issue can become quite frustrating.
The issue started when suddenly I noticed my keyboard acting weird and typing the wrong keys. It seemed as if my FN key was stuck, so I could not type the normal keys without holding FN.
It turns our that the problem was not the FN itself, but actually the Num LK key was on (I must have turned it on without noticing). This means that your num pad keys are active by default: (U)4, (I)5, (O)6, (P)*,(J)1, (K)2, (L)3, M(o).
In my case, I have an Dell Alienware M15x system. My Num LK key is on the DELETE key, and it is activated by pressing the FN key + DELETE at the same time.
This might sound quite a stupid mistake, but after searching online for a bit, it became clear that there are LOTS of people having the same issue. That’s why I decided to post this.
So remember, if your keyboard starts typing the wrong keys, it might be because your Num Pad is on!