Don't overtighten the set screws -- snug only as they will crack the spine if overtightened. Use Loctite Blue to hold them in place. Make sure your screw is in the slot. That will fix your problem. The plastic warning is not an issue with the type of materials Hobie uses. I Loctite everything on the boat and have for years -- never a problem with it. Hobie uses it as well.
DON"T use Loctite Red unless you intend for it to never come apart!
The only exception to Loctite Blue is the older Drives with V-1 masts that are wobbling. In that case I use Marine epoxy to reset the masts and also with the set screw. When that fails it's time to upgrade to V-2 sprockets and masts!