Had problems with my Ev2 after a mishap when the barrel got bent. I had to return to having the barrel clamp put back on after having it floated because I couldn't get a decent zero within my scope range. I noticed a few shots going astray similar to yours and after investigation found the collar screws to have loosened causing the barrel to effectively move about. Tightened these up and made sure it was located into the stripper and has been ok ever since. For top job on Ev service see Dyno Dave on here....top bloke.
Hope this helps Keith