RE: ESM Spitfire 72.5
Here's a picture of the retract. The set screw doesn't clamp down on the retract, instead it's just a "key" for a slot in the strut housing to prevent twists. I think I know what you're talking about, Tevan, and that's something I'm definitely going to do on my electric retracts for my Deuces. This one is different, the gear axle isn't the part held on by the set screw.
To be honest, I have no idea how it came loose. I think it's just crappy hardware.