I have tried reading other posts on this topic but I'm still unclear how to diagnose this problem.

I have central locking on my 2002 Fabia. Key only - not remote. When I turn the key to lock, all the doors lock and then instantly unlock.

To secure the car tonight, I have entered through the passenger door, used the internal central locking switch and closed the door. This worked OK - all doors locked.

Tried WD40 in the keyhole to no avail. Anyone got suggestions or similar experience ?

I have the same problem did you find out what the cause/solution was?

try my post here:

http://briskoda.net/forums/fabia/central-locking-alarm-problems-tips/113601/

and this if you want to attempt repair:

VWvortex Forums: MKIV door locks explained - why you're having problems!!! :(