Just took another motor apart this morning that has several issues, I'll post step by step instructions on how I go about repairing it.
Remove the motor from the housing (scroll down to see assembly process and reverse the order), next remove shear key from the slot in the axle.
Remove the half clip
Remove the 3 screws, they are tight so take care not to strip them out.
Slide the gear off
Use c-clip pliers to remove retainer
Place motor on a hard surface and push down on rotor housing to overcome the magnetic field.
It should slide down and off the shaft, note, you really have to push hard to do this. - Careful not to lose the thrust washer
push on the magnets, if one slides down you know they are loose, or if it makes that grinding sound just assume they are loose. Number each magnet so you put them back in the proper order
With a screwdriver you can pry up the magnet to remove them
Safe spot to store them is on the outside of the housing, be very careful handling the magnets, they are strong and if they slip out of your hand and snap against each other or a metal object, can easily break
Once they all removed, clean all debris and old glue from housing and magnets. I usually give each magnet a good cleaning just before gluing it down.
this one had several issues, the other being a cold solder joint on one of the halls sensors. Note the 3 in the center of the picture, the middle one is loose causing erratic running of the motor.
Starting the re-gluing of the magnets (using epoxy: buy on Amazon)
All done, note magnets are flush to the outer edge of the housing. Now to wait 24 hours for the epoxy to cure
Just showing how fast the stator snaps into place
Install snap ring
install gear and half clip
slide assembly back in housing
Once fitted give it a spin to insure all is well. There should be a spacer and thin washer on the shaft.
install cover and 6 allen screws, Note this is a spare motor housing, the reason it isn't laced into a wheel.