Yaeh! I noticed that set screws for those ebay pulleys are way too short. What is your belt width?
Mine were perfect but with mine being 10mm shaft I’m guessing they are using the same screws from the 8mm to the 10mm.
If you have to remove the pulley dont use loctitte (to remove it you will have to put some stress on the axle, thus to the motor; it can be both mechanical stress like hammering it or thermal shock like using dry ice) A clamping system made of 2 screws (this system is meant for 3d printers)is not quite effective as a keyway system( a keyway lets you spread the force over 27mm2 surface, if you use a 18mm pulley).
One half way between the screw system and the keyway system would be the following: you will have to fasten the screw down into the keyway of the axle.
Pros of this alternative: much more clamping force than the only-screw system
Cons: 1)you will probably wear off the keyway in the long term. 2)this is not as effective as a key system.