Open and shut the door? Sounds like a bad connection or bad earth, possible earths down by the osf kick pannel loose if there are any down there and moving when you open and close the door. I know the mk5 escorts suffered with bad fuse box problems causing electrical faults but dont know if this also happened with the mk6.
If you manage to find the fault and req parts I am breaking a R reg Gti and selling off the bits if that helps.