I just went through something similar, but mine would cut out and die and finally it just quit running if you did anything like move the throttle.

Mine turned out to be crud in the carb. I took it all the way apart and cleaned it up and reassembled. It run fine and today I flew it for about an hour with no problems, in fact todays the first day I've been able to get more than 2 flights in on it.

Mine was a ZDZ and a Bing carb, but all carbs can get dirt in them, especially if you don't filter the fuel. I double filter mine before it gets into the tank so the tank stays clean.

Anyhow, I vote for a passage with crud in it.