Hello fellow 850ers!

I've been hunting down three short circuits in my 1996 GLT Wagon but can't quite pinpoint the source: The rear wiper (fuse #33), rear defrost (fuse #11), and central locking (fuse #6) fuses all blow immediately after being replaced. Looking at the wiring diagram, all these circuits go through the tailgate, and all seem to share the same ground (g404 on the wiring diagram). However after taking apart the tailgate and interior panelling I haven't been able to find any obviously damaged wiring or find the grounding point g404.

PDF of wiring diagram (I used ctrl+F to find "rear wiper"): https://www.volvoclub.org.uk/tech/se...ngDiagrams.pdf

Has anybody experienced a similar problem and does anybody know where I might look next to get to the bottom of this one? Thanks in advance!