I have a Mossberg 590 pump shotgun. The action lock lever on keeps getting stuck depressed when I push it.?

I just bought a bran new Mossberg 590 12 gauge, 9 round, pump, home defense shotgun. Whenever I push the action lock lever on in, it stays in, allowing me to pump the shotgun, but doesn't return when I let go.. To get it out I have to pull it back out with my fingers for it to lock the pump instead of it returning on it's own. I took it back to the guy I bought it from and he oiled it and it worked for a few minutes. When I got back home I tried to lubricate it as well, but it's still having this problem. Is this just because it's new and not broken in? What can I do to fix this problem? I used break free CLP and LP to try and lubricate it and it would only work some of the time at best.