Hatsan Edge Vortex .22 cal

Have a problem with my Hatsan edge .22 vortex, when zero is on will do dime size groups at 25yds but my scope rings keeps sliding back and shears off the stop screws moves with two piece rings or 1 piece rings. Any suggestions on how to remedy this will be greatly appreciated. It has about 1200 pellets through it so far.
Thanks
Grumpy