Door light
I just went thru a headache on my MK5 (I realize yours is a MK4) where my dash light (open door) would come on intermittently. I had a new door harness and a new lock module and still had the issue (I had multiple issues - some were fixed with these repairs) The light on the dash seems to have been fixed by replacing the window motor. On the MK5's, there is a control module for the door built into the window motor. I grabbed one from the self service wrecking yard, swapped and so far, the issue has been resolved.
(I was able to diagnose this part, in my circumstance, by having the door panel off. The light came on the dash and I applied some "percussive maintenance" to the window motor - control module. The light went off the dash. This happened a few time for me prior to dropping the $20.00 for a boneyard part.)