DM2400 motor gears

Tonight I removed the motor cover off the Z Axis to pull the drive card off and put new JTS connectors on in prep for the Gecko drive. Here is what I found, When I turned the motor shaft it turned freely no resistance and no up and down. I pulled the motor and found the small 10 tooth gear was loose on the shaft. I got an allen wrench and could not tighten the set screw. I ran a M4 tap down the hole and cleared some burrs off the treads and the set screw will now engage.My question is: Would the set screw be restricted to tighten all the way to the shaft in order to prevent a stripped plastic gear in the event of a crash? I wonder if it was manufactured like that and I have now caused a bigger problem.
Thanks

I reread this and it wasn't clear. Obviously the set screw would have to be tight enough to engage the shaft. What I meant was the set screw would contact shaft only enough to allow it to shear in the event of a crash, thus saving the plastic 100 tooth gear.

No the gear would need to be tight to the steppers shaft. If the gears breaks, so be it.