Yep, common after 2 years here in Hawaii with our bright sun. We've gotten it to last a while longer using just clear shipping tape but others have used tape made for sails.
We are lucky here, to have many wind-surf sail makers so we have had all the clear panels replaced in a few AI sails for only $100us each.
We now use either 303 or Hobie UV Protectant to coat the sail, 3-4 times a year here in Hawaii, probably only once a year most other places.
- - - - - Hobie Island Sailing since 2006 - - - - - 2011 & 2012 Hobie AIs and a 2012 TI