Question
Hi Matt, our sprinkler is a rainbird 3500, and it stops turning the 3rd time. We are pretty sure it isn't caught on something, or stuck, so could you please help us find out the problem? Thanks a lot.

Answer
It appears you have a bit of debris in the sprinkler. It could be iron in the water or a hard water. Trying to clean it out is about impossible. It inside the sprinklers gears.
I suggest getting a new sprinkler and just replacing it. It will be less frustration.
Sorry I couldn't be more help.

Matt