Made an account on here just to share this.
I tried all the steps above, save for repairing, but I figured it out (maybe).
In the controls I clicked the 'default' button on the Gun Trigger command. This turned the command red which I'm guessing is DCS telling me there are 2 functions bound to the key.
Then I found out I had space bound to VR zoom in the UI Layer section. Unbound that and it works now.
Hope this helps somebody.