This flap is the one at the centre as the air intake hose crosses the top of the engine under the engine cover on the 1.4Tsi 160ps. I've already disconnected the air filter end of the hose to look at the flap, and seen it's still able to rotate fully when cycling the ignition on and off. So it seems to be more of an intermittent error. It doesn't always occur when driving and when it does, it can go away if I wait 10 miles or cycle the ignition. But when it does go into failsafe, apparently the flap remains open so the air goes straight to the turbo rather than going through the supercharger first.
I've checked the wiring (as have had some sort of rodent nesting in the insulation under the bonnet!
) and it looks to be in good condition, but the resistance across the motor is 2.6 ohms which seems to be a little low (spec is 4-7 ohms). I'm not sure how to check the voltages of the control circuit when it's operating, as there doesn't seem to be a way of inserting probes into the back of the electrical connector - with the cover off the connector I can't see the back of the pins, only some sort of resin holding the pins in 
I've looked at biting the bullet and replacing the whole part, but from VW is £473 - eek! - or there seem to be a variety of remanufactured ones from £213 going down to £51 (somewhat questionable looking Chinese one). Part number is 03C 128 063B
According to this factory manual https://workshop-manuals.com/volkswagen ... _article=1 it would be a doddle to replace it myself. It even seems I won't have to recode the new part to the ECU/relearn basic settings if it is a plastic one - I'm not sure why that is. Does that seem correct, as I would fall at the last hurdle if I then needed to find someone who could do that for me on VCDS?
There seems to be a lot of discussion online that some errors with this flap are likely caused by oil being sucked into the breather pipe, passing through the unsealed bearings of the flap motor shaft and slowly saturating the flap motor. There's even a video of someone repairing theirs by drilling a small hole in the housing, using brake fluid to flush out the oil, drying it out and resealing the hole: https://www.youtube.com/watch?v=R5Pnho5P-Uo. But that was to fix a P10A4 fault ("Intake air flap control actuator mechanical malfunction"), rather than my "short to ground intermittent" fault.
I was wondering if anyone else had any experience with this fault and there was any other way of addressing it. To me it seems strange that oil can cause a fault which goes away when removed, as oil isn't a conductor? Or would it be causing breakdown of other insulation materials or something? If my flap works and it's an intermittent ground fault, is the fault likely to be in the wiring elsewhere - as if so, it's not worth spending even £200 on a part to find out! Or is the low resistance reading I'm getting from the motor a good enough reason to stop there and splash out on a new one?
Any ideas welcome. Many thanks in advance!