Are your screws loose? Check your motors.

The first thing you should do when you get new motors for your quadcopter is to check to see if the manufacture put thread lock on the set screws holding it to the motor shaft.

I noticed my QAV250 quad was flying really strange. It was having a hard time flying in a straight line without random yaw drifts. Anytime I punched the throttle it would go into a crazy yaw spin. I was tuning my PIDs so I just ignored it. Then my quad just started rolling out of control and fell onto the concrete. I was surprised it only broke an arm because it took a pretty hard hit.

Upon closer inspection, a set screw had come loose during flight letting the motor to spin freely on the shaft. When I checked the other motors none of the set screws had any kind of thread lock and they were all loose. Seems like this is a common problem with the SunnySky X2204s-16 2300KV motors.

There is a simple fix for this. Use a tiny bit of medium strength blue threadlocker, like this. Make sure you use blue so you can remove it later if you need to. Red threadlocker is permanent. This stuff can get pretty messy if you try to drop it straight from the bottle to the screw. Instead, you can put a drop on some plastic and lightly dip the screws into the drop. One drop is enough for all four motors.

Go check your motors! I bet you have at least one loose screw.