I have an XD40 Service and I am having a problem releasing a loaded magazine. It was a little stiff when I bought it, but seems to be getting stiffer, I tried some oil on the internal release mechanism, but it didn't help. If the slide is locked back or the magazine is empty, no problem. Seems the less rounds I have in the mag the easier it is to release. I believe this is a hint, But to what I don't know. Any Ideas?