feedback circuit on battery powered dremel? repair

[CopperCone]

So I was brushing rust out of some nooks and crannies on a vise I could not get at with any other tools and my dremel halted, I thought the battery died or it overloaded. I was just using a mini brass brush. I typically use a dremel fan accessory with it so it blows away the dust from the air intake ports.

I charged up the dremel pack and it did about 1/2 a turn and stopped. When I attempted to power it back up after it stopped it did not respond.
It was not hot or being used heavy at the time of failure, just very gentle brushing.

 Likely failure modes? I can't find much on the battery powered dremel repairs. If there is something likely I would like to try to repair it but I don't know if maybe trying to get the company to repair it is a better idea.

I thought that maybe there is some sort of thermistor or NTC inside? I don't know why a motor control would do 1/2 a turn and stop spinning unless something is over loading.

[CopperCone]

Well I spun the shaft when it was turned on and I saw a spark inside. Please be a bad wire

[CopperCone]

open circuit on the motor and the motor is a bitch to open so its in limbo right now till I am assed to get a pair of dykes to try to open it up 

[CopperCone]

ok I took the motor apart. It only has one brush and some kind of black conductive shit was inside of the chassis, the motor brush spring thing looks ripped, and one of the cooling fan fins is missing

I think basically what may have happened is the cheap brass bushing ripped apart, the carbon brush hit the rotor, then it got thrown out in to the chassis. 

who designs this horse shit