door lock problem seat ibiza

Hi, I am having problems with the locking on a 2005 Seat Ibiza. The drivers door opens and locks as normal, but I am having trouble with the other 3 doors, especially left rear. Generally after a couple of minutes of messing around pressing lock/ unlock it locks fine. In the last couple of weeks though the left rear door has taken longer to lock, sometimes having to be left unlocked over night. Does anyone have any ideas about resetting the locking or any other solution? Thanks.

I have the same problem with my car which happens to be a Seat Ibiza from 2005

lukec233 (from 2014; sorry i wasn't around to see this), and
haryhanne (from this evening)-- welcome to Automotive Forums
(some way more tardy than others)..
hary; i hope luke already figured his out, but ibiza's do have a reset
for the door locks.. it is:
turn ignition on to POS 2 (red lights on dash)
turn ignition off immediately! and pull key out
While holding/depressing one of the buttons down (doesn't matter which), press the other button 3 times (with a slight pause) 1,---2,---3,--- ..
Watch the LED on the fob (it should flash) and the doors usually try lock/unlock.

and while unfamiliar with all SEATs, for my Audi and SAABs, the antenna assembly is
tucked under the trim panels of the back rear door frame..
i have opened up many an Audi and Saab, and unbundled their wire/antenna (which is usually just bunched up and zip tied directly near the receiver box) and tuft the 2-3ft of wiring, and run it up the pillar towards front of vehicle/sunroof; under edge of headliner.
this; i have noticed, increases remote activity to almost a football field (american; not futbol- rest of the world): 200yards/metres..
hope this helps..