Golf door won't close

[groomi]

Just opened the rear drivers side door on my wifes MkIV Golf and now it won't close again. The latch doesn't hold the door closed.

I'm guessing the latch is sticking, but could it be a broken spring or something. Anybody know if this is a common problem and how to sort it?

I don't want to leave the car unsecure overnight.

[Tame Technician]

They do do that in this weather, partially frozen.

Boiling water from the ketle then a good spray of WD40 or similar.