I recently purchased a Glock G21. When I cleaned it for the first time, I noticed the spring and rod weren't in the half-moon socket. I put it back in, and went to a gun range to try it out. I noticed there was some weird recoil reverberation every 8 shots or so while shooting. When I cleaned it a second time, I noticed the rod was again out of the half-moon. I replaced the spring/rod with a new one purchased on the net and I running into the same issue. Is this normal or should I call up Glock?