Has the motor or gearbox seized? That would cause loads of sparks due to the high current draw!
The brushes in the photo look a bit short too, are they contacting the commutator properly?
I can see two wires in the photo, are they just for the switch?
Good luck with it.
Great morning read with a coffee.
The brushes seem to be in good shape and contact the commutator well. When I had the motor apart, everything seemed to be working properly. Yes, those two wires are for the switch and simply connect the pos feed.