Recently purchased a used 12 gauge nova from a pawn shop. Was cycling rounds through it after I brought it home and noticed the pump does not lock when the gun isn’t cocked. Might sound weird but if I pump it once the action stays in place like it’s supposed to. But if I fire it the pump wants slide back on it’s own. It’s annoying because I have to hold the slide up while chambering the first round otherwise the slide is too far down to insert the first shell into the tube. Any ideas on what it could be? Wondering if I should try to take it back?? Thanks for the input.