I just took delivery of a Gantry Crane (76500)-- generally a very impressive item and works well with one notable exception.

The contact points both on the Crane Bridge and the Crane cab itself are extremely flimsy -- clearly Marklin recognise this as they supply spares for both in the box.

Even after a few try-outs it looks as if the contact points on the Crane cab are going to need replacing -- they're starting to bend back and look as if they are about to snap-off.

Has anyone got experience of doing this replacement themselves, which looks reasonably straightforward, or is it a back to Marklin job ?

No, this is clearly not necessarily a Märklin job, I've conducted this minor repair myself several times. It as simple as unscrewing 4 (if memory serves) screws and soldering one single wire.
Took me less than five minutes.

Hope this helps!