I found that, with the Awesome Filament Spool Rewinder - Upgraded, the axle underneath the sled, when printed, was too tight. So I had to shave it a little to fit in my bearings. This got everything fitting, but at high speed (with the motor), the axle could start to slide out of alignment, until it pulled itself from the drive gear.
I made this bracket (using the rewinder main body as negative space) to act as a clip that can be applied to the rewinder after the axle is fully installed, and will prevent it from sliding out if the fit in the bearings, like mine, is now slightly too loose due to shaving.
The author marked this model as their own original creation.