My brother just got a Fabia SDI (X plate) - when reversing uphill (not on flat!), reverse gear pops out.

The car's done 131k.

No problems selecting the gear, the rest of the gears feel fine too.

Any ideas on what we can do to fix this?

Cheers

Does it pop out if you hold it in?

Nope!

Does it pop out when your travelling along with your foot on the gas (in reverse) or does it just do it when you lift off the gas?? Could be a knackered dog-bone mount.

Yep, I'd say one of the engine mounts.

I only ever swear when I pop out

Thanks everyone for the suggestion, and b1ackb1rd for making me laugh . We'll investigate and order the bits if necessary!