Sloppy, shuffling feet

Working with a young athlete (13) whose feet are everywhere but going straight ahead.
He’ll run fine for 10-15 meters, stepping over nicely, landing on the ball of his foot, then his feet will externally rotate and start striking on his heels. Could this just be overall weakness in the foot/ankle/hip.
He overpronates but wears orthotics. 5’3 140lbs.
What can be done? I don’t want him to develop bad habits.

Thomas i would build the athlete up steadily until he can maintain proper contact throughout that i mean build up the distance and if needed drop the effort.if he can run sound for 15m then adjust to 25m and build from there until he can run those distances fine.whats he like during strides or jogging?

He falls apart while running any distance over 75% effort.

exactly get him used to running at 75% and move up the % sprinting a new movement to him.if an athlete is falling apart it usually means build up of lactic caused by tension or basically not being accustomed to the movement at a higher rate.take my advice and tell me the deal after 3weeks!