I bought a new 9mm compact and have yet to fire a round because of illness. I'm becoming familiar with the gun and having problems with engaging the slide lock to keep the slide open. I've managed to get it to engage and lock the slide a few times so I'm thinking this is a user problem. It seems that the slide lock lever is not pushing up as it should. I've disassembled the gun and the slide lock lever pushes up fine. Any advice?