Dodgy Sliding door locks?

[CovKid]

It seems to be a common problem as soon as the temperatures plummet. My observations of this is that the grease in the rear catch becomes stiff in colder weather (don't we all) which means the catch doesn't move fast enough during the closing sequence and when you think you've shut the door, it hasn't actually grabbed hold. Had an identical problem on a MIDI van which is why I figured the cause. I've not tested it yet but during the summer I washed all the grease from it and used light oil instead. I have not so far had a problem but sometimes it doesn't happen until theres an actual freeze. Sometimes a slower close helps it catch properly. If it won't close, slamming it doesn't help either - just makes matters worse. Slow but firm shut will often solve it.

Hope thats of some help.