My awning is 15' (A&E Sunchaser) and I turned it 12 times. It works well now. I can hear something rattling around in the front spring area of the roller tube, but it does not seem to affect the operation (yet).
12 turns on a 15' is about right and glad you backed off a little. As long as it is working, I would not tear into the tube to find your rattle. Sounds like a broken spring, but you say it is working, so I wonder.
this was helpful for me also, however i have one other issue. I had to replace my whole awning due to storm damage, and the front most screw will not tighten for the top arm bracket any fixes for this?