A quick update. Despite me selling the truck, I changed the motor to a Leopard 4092 1730kv motor. Even on 6S, the outdrives lasted quite fine and did not break again.
I guess it was just the massive torque of the psycho outrunner I had in the truck that ate outdrives like M&Ms. The psycho outrunner has been traded with a friend and he'll be using it for speedruns