I had the rotting/crumbling problem also on my deck installed August, 2004. After I contacted them and jumped through all the hoops with descriptions, measurements, pictures, etc. they sent an inspector and eventually agreed to replace the materials. Nothing offered for labor of dismantling and disposing of old, and installing new. I did not sign their agreement and asked for a possible refund. They the offered an insulting $133.92 in addition to the materials. I don't think that money would even cover the new screws. There is a possible new class action suit for decks installed after July, 2004. I'm looking into it.
George F

We have the same problem. Our deck was installed Aug of 2005 and by the next summer there were no gaps. It's a pool everytime it rains. Trex suggested "kerf" cutting, but even the people they recommended thought that was a bad idea. I've had three people recommend getting a new deck. I'm also looking for advice. I believe Trex should be accountable, but from what I've seen on the internet I'm not hopeful.

I, too,have had the same issues with my Trex ("redwood") deck. The rep will give you the boilerplate reply, offer a cleaning solution, but the mold spots will return within 2 weeks. They know they have a problem, but won't deal with it. I have also contacted the BBB. There are 2 class action suits that are supposedly in process, but no word yet.
May I have your email so we can band together?