I'm afraid I don't have any other ideas. It seems like you have tried everything but the problem persists
It is most likely a software problem and you will have to minimize (remove) items that are running until you locate one that is causing the trouble. Or a smaller chance is some hardware problem, such as something acting up once it is hot from running a while. Either case will require a lot of trial and error and there is nothing really more I can do or suggest to help. Sorry.