84 380SE MB alarm & Trunk lock

[SNBmerc]

'84 380SE:
Ever since I got the car - at 193k - the electro-mechanical Trunk lock has been activating / de-activating every time I locked / unlocked the car at the Driver's door (apart from the time the battery went flat and the jump leads were in the boot, so dumbo here - who'd left an interior light on - had to borrow leads AND a jump battery).
Only just now the electro-mechanical lock stays activated, no matter what I do with any key / door lock combination. I've had to find and use the emergency pull handle, pull the electric servo unit out and somehow get the unit to stay in the open position (earth the black / yellow wires with unit plugged in). It's not the servo unit - another unit from the breaker's does the same thing, so I've left it dis-connected for the moment.
Any ideas on what's happened - and what it needs to fix it ? For the record, I'm aware it's *supposed* to have an alarm, but I've no idea if it works or not - never known how to test it. The tic-tock from the passenger footwell is still there whenever a door / trunk is opened and closed if that's any help.

Other than that it's great - 234k miles and burns half the amount of oil than the 127k mile '89 420SEL we have.

[mbdoc]

The 1984 USA car was the only car with that system & it NEVER worked well!
Takes 2 people to operate the emergency release, one pulls the cable while the other uses the key & pushbutton on the deck lid.

[SNBmerc]

Figures. So it'll stay dis-connected.