Orman,
My understanding is that the fabric is "Sunbrella" and will never rot. The thread is not, so it rots.
As a DIY fix, I stitched it myself. I found some heavy duty black "outdoor" thread at Joanne Fabric and a curved "upholstery" needle. It took a view hours, but it came out OK.
If you want a more processional job, it is fairly easy to remove the fabric. It is a lot less work to slide the fabric out than service a HydroHot! The trick is knowing how to completely unwind it and put a screw driver in a locking hole. That takes the tension out and makes fabric removal easy. The primary concern is to be sure you have the roll up locked and keep your fingers out of the way in case it is not locked! Once the fabric is out you can take it to a marine awning shop where they have HUGE sewing tables.