It's the seals, they are rubbish, it's quite well documented for years.
We fitted "OEM" both leaked almost straight away. Out of principle I made the supplier refund the money.
Bought 2 NAK seals, damaged one as they are a very tight fit into...
Next bit I've got photos of is my vacuum CDL
Untitled by Steve Goodwin, on Flickr
Untitled by Steve Goodwin, on Flickr
Next up long life ride height sensor link rods
Untitled by Steve Goodwin, on Flickr
Untitled by Steve Goodwin, on Flickr...