Hi, as Stephen says, its a common issue with C5 seats, luckily it is also a cheap & simple fix (although doing the 1st seat takes a lot longer than the 2nd as you know what you are doing by the time it comes to doing the 2nd one).
I did mine a few years ago & I've attached a couple of links that you might find useful.
I think the first link talks about buying a seat repair 'kit' but in fact all you will need is a set of 8 (to do both seats) [FONT=Arial, Helvetica, sans-serif]
nylon washers total. 3/4" OD, 7/16" ID, 1/8" thick . I bought mine off ebay for pennies. I then used a piece of sandpaper flat on the floor to sand them as required. It takes a bit of time but its worth it. I think I followed the Lieblweb link as I had it open on the ipad in the garage & I could scroll down the page keeping the picture I was working on open before moving to the next stage. The video gives you an over view of what to do, I just found being able to pause on each stage was easier.
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The most important point was getting the seat up & forward before removing as it makes it a hell of a lot easier to get everything back together.
Again as Stephen said there was a recent Wheeler Dealers on this fix but I still thing the lieblweb link on an ipad in the garage whilst you are doing the job is a whole lot easier to follow.
Good luck.