From my personal experience, it sounds like a it could potentially be overheating. I've had a chugger for 2 years now and it's still going strong. When I first got it, I put it in a toolbox like some of the folks on here built. In the summer, if the lid was closed, that caused the pump to overheat and stop running. Now, I just make sure it has enough airflow around it to keep it cool when it has hot wort running through it. Haven't had an issue since, but I am mindful of it too.