Richard,
I have a 12 ga Repro Magnum that did exactly the same thing last year on an October Manitoba canvasback hunt. It only stuck the first time the gun was open, same as yours. It also seemed to stick on the coldest (not wettest) days. I squirted some gun oil inside and worked the action and safety. I even took as much of it apart as I dared. After a few days it worked fine and I have not had problems this summer on the skeet range or up north this past month. So I am not quite sure what I did....(how's that for help?) but lube and working the safety seemed to work for me.
Regards, Steve Kleist, Ely, MN

Thanks Steve. I figure I'll see the problem when I dismantle it. I want to seal inletting up anyway as I always do if it's not already sealed. Some of the Repros seem to have acraglass or something in the inletting that seems to seal them pretty well. This safety was REALLY sticky. I had to shove it against a tree and push it off at one point... a little excessive I'd say and embarassing to say the least when the guide gets you a good flush and you miss the shot because of your safety.... not good. Seems like a more common problem than I realized. The posts from everyone are a big help... as usual....

Many Reproductions have had this problem. I was led to believe that the grease / oil that they used during assembly easily turned to a sticky goo. The solution was to take the stock off and liberally lubricate the mechanism and wipe it down. Then use a light oil coating.
It worked perfectly for me.

Thanks Michael. I'll be taking it apart at some point and doing something like that. Have never cleaned it yet so it's got to be due.

10/30: It's had ample time to dry out inside and now it works just fine. We live and learn... Thanks to all those who gave input.