Centerfire Savage 840 bolt problem

I have a savage 840 30-30 that has been in the family for years. Recently I decided to get it out clean it and use it for the upcoming deer season. After cleaning I took it to sight it in for about ten shots it shot really well. The bolt then started sticking shut after each round. had to give it a good rap with my palm to get it open. When I got home I decided to clean the bolt some more and was planning to go shoot some more to see if this helped. Then it would not break over and lock when closed. Close it hard and fast and it will break over. If i reach through the mag well and push up on the bolt it will break over and close. So there is a flat piece on top of the bolt with a little flipper piece under it that depresses and lets the bolt rotate closed. Could this piece be causing both problems? My main question is what is that little flapper piece called and how do I get the flat piece off the bolt to get to it. Hope someone can help did not see many posts about the 840 after searching for over an hour. Thanks for reading Twilly