Thanks for the picture!! I’m going to guess that the left hand supports are twisting away from the motor just enough to let the axle out.
I’m going to assume there is a bearing block on the otherside of the two screws. (If not, there should be. There should be enough space to slide a collar into the gap between it and the motor. A little hard to get to, but doable.
Can you put something across the gap between the two supports, like some 1x strip to hold them together?