I'm fairly sure the problem is that rainwater seeps into the seam between two segments and runs down the plies. I've tried to seal the upper edge of the segments with paint but it never stays. When the door is all the way up or down the segment edges come together (touch) and the paint sticks to the other edge and is torn/pulled off when the segments separate while opening/closing. I've tried sealing the edges with this stuff and injecting it into the paint cracks before repainting http://www.minwax.com/images/Products/hardener.jpg , but it doesn't seem to do anything at all. I have also injected caulk into the cracks.
Here are the best pictures I've been able to make to illustrate this problem, but they don't make it clear.
Note also the bolts that are rusting. I've replaced most of the rusted bolts over time. I always to seal the bolts from water by filling the bolt holes liberally with caulk, to the point it squeezes out in all directions. It helps, but it doesn't prevent rerusting.
If I can't come up with something this time that works I guess I'm going to have to replace this door that's in good condition otherwise.
Anybody have any new ideas?