okay i just pulled mine out to refresh myself with it. Seems to me that if you short stroke it it will not lock closed. try pulling the slide all the way back with a little authority then closing the action. My first thoughts however is that it is time for a complete disassembly and cleaning. Is this the one that was in the EE open to offers? if so message me I maybe interested. Let us know if this helps regardless though and I'll keep playing with this one and see if something comes to mind.