Hi guys,
Couldn't see anything online and managed to fix my issue so thought I'd share. Basically the small shade over the rear door glass was not retracting well on one side and not at all on the other.
To solve I removed the shade mechanism (just pull them hard and they'll pop out) then took them apart a bit.
First, pry along the blue lines (pic 1) and take the foam/clips piece off which will give you more room for the next part. Bare in mind you will need to glue it back so you can probably do it without this step.
Second, push the metal piece down and then pull the roll of shade out and away (you'll find the metal piece spins) (pic 2 & 3)
You then need to pull the metal thing out a few mm and wind it anti clockwise until the shade is tight. I did this with pliers and then pushed the metal end back in the slot and it should stay.
If this is done correctly and you have no other problems with the spring you should have a retracting shade again. It's a difficult one to explain but I've tried my best.