Glad you caught it and fixed it quickly. Nice job.
We had a similar problem two weeks ago. While closing the awning, the front rafter support arm felt loose. I looked up and sure enough the rivets did not seat well in the newly installed panels.
I had some parabond and thick screws sent and took off the bracket, cleaned it up and resealed the holes filing them with parabond before drilling down the screws. I'll get it done right this fall once we are done with it.
We've had some very heavy rain on the east NC Coast here and no problem with any leaks.
Here's the before picture which I'm glad we were paying attention to when closing up the awning until the next weekends get away.
On this old bracket, the front bottom rivet hole, only takes rivets, so attempting to place a taphead style screw in this will not work. The rafter arm will NOT seat correctly. Found out the hard way by forcing it down and now the ear of the bracket is cracked. The Zip Dee awning fared well for 35 years until this repair. We'll get it fixed in the fall.
Too much fun to be had.