neu motor shaft coming out?

[t-maxxracer32]

hey im not sure if this is a normal thing but the shaft is starting to come out and so it is making me strip my STEEL spur gear...

i have to take off the mount and hammer it back in. im guessing this is not a smart idea? ive only done it twice so ihope i havent screwed too much up.

let me know if theres anything i can do.