I haven't read about anyone else with this problem, but my 66-plate MK7 parcel shelf seems to have a weak spot - it's hinges. These are two-part plastic items with a small bit of springy plastic that secures the shelf to the plastic dowels in the side panels. One of mine broke and rather than shell out £130+ for a whole new shelf I did some googling and found the following part number: 5G6 898 780
That gets you left and right hinges and two strings. The hinges are a 5-minute job to change. Not sure about price from dealer but I have seen it listed on ebay for around £30.
Hope this helps someone.