Possibly one of the multi-contacts at the front edge of the doors and the A-post needs a clean. These need to make as the door closes so the rear actuator knows to pull the back of the door in. If the latch misses for any reason the door will open again. I clean mine about once a year. They can very occasionally break contact as the body flexes on bumps.
Use fine sandpaper - the sort you might use for the last rub-down before house painting. You need to take off any surface dullness and end up with a shiny smooth finish. Don't be tempted to use a file as you could short across the contacts and blow a fuse; sandpaper is quite safe.
Do pay particular attention to any black spots, they usually appear on the fixed A-post contacts. The reason for using sandpaper and not emery or wet-and-dry paper is because the hard bits of emery might embed into the metal and then you would have created more problems. Afterwards just wipe off with a clean cloth; no need (in fact best not to) spray anything on them.
As the cars age, bear in mind that it is possible the connectors on the backs of the multi-contacts are deteriorating both are only held on by a single bolt so it may be worth while taking them off and cleaning the plugs and sockets behind.
Next, check that the outside door handle has returned fully forward under the action of the internal spring. Pull the handle right back; release so it springs forward without help - and then check it won't move any further forward. If the doors are usually operated from the key-fob then over a period of time the outside mechanical handle can become stiff because of a build up of oxide on the hinge mechanism. This can cause the handle to stick in the 'partially open' position even after you have let go. To fix this, spray the pivots with WD40 penetrating oil from time to time to reduce the oxide build up.
Also double-check there is nothing dropped or jammed in the door aperture that could possibly stop it fully pulling in. Also try "helping" the door to pull in by pressing the back of the door inwards as it closes.
Unusual - but on a very hot day, a door distorted slightly, causing the TOP locating spigot to HIT the socket instead of sliding in - the electronics sensed something was in the way and the door opened again. I chalked the spigots to see what was happening and could see where the chalk was left on and around the sockets. Ten seconds with the socket set to adjust the top spigot and no more "won't close" door problems. :-) This would be consistent with a "permanent fault - door contacts" indication on PP2000 as clearly the contacts never actually made.
It is helpful to drop a little oil or spray grease into the catch at the back though generally they don't cause problems. Do NOT lubricate the door rollers or the guides.
perhaps obvious, the catch at the back of the door (that latches onto the rear actuator) can be accidentally flipped over so the door lock catch cannot get hold of the hoop (see pictures below). This HAS happened to someone after servicing - he hadn't realised he'd flipped it over. Clear simply by operating the external door handle; you should hear the catch click back.
A few have found the in-door actuator sticks in the fully retracted position and the internal spring isn't strong enough to push it back out again; this prevents the door lock working. This means that, when the door closes, the lock cannot grab the B Post Actuator so registers a "fail to close" and opens again.
Very occasionally, the door lock catch may not latch on to the B-post actuator. It may be that a small outward adjustment of the B-post actuator is needed to ensure the door lock catch can get hold of the loop.
A few have found that the B Post Actuator, after moving outwards to release the door, then pulls back in. This means that, when the door closes, the lock cannot grab the B Post Actuator so registers a "fail to close" and opens again. This MAY need a new B-post actuator, although one or two have simply reseated the plug in the socket and all came good.
one final thought - after you have tried everything else above. A few have found that if you pull the cable attached to the in-door actuator too hard - the lock at the rear of the door can occasionally jam in the unlocked position. A solution to this is to slacken the lock mounting screws (not too far, just enough so you can move the lock assembly a little). You may be lucky and hear a click as the lock unjams (is that a word?) - and retighten.
Left door lock
If the lock catch doesn't get hold of the hoop then the door won't pull in and the electronics will signal a failure.
Right door lock
If the lock catch doesn't get hold of the
hoop then the door won't pull in and the electronics will signal a failure.