HAWKE SW 30 ELEVATION TURRET CAP PROBLEM

Hi
I´ own a HAWKE SW30 scope. Last weekend I was setting my scope to various distances and when I try to reset the elevation turret cap to -0- I notice that the cap does not lock down. I remove the cap and check on the turret, it was working perfectly. I put the cap again, tighten the upper screw and again the cap does not lock, it keeps spinning. I check the inside of the turret cap and nothing seems to be broken.
I need some help here guys, I would really appreciate it.

Regards from Mexico

José Palma