Thought I might tack on to the end of this thread... my bold had a tendency to do the exact same thing. I told myself I wouldn't let it bother me, but it kept on doing it. Figured something had to be done.
Tried putting thin pieces of cardboard at the top part of the battery assembly to jam the battery in there. It doesn't work, as the upper portion of the edges of the battery is receded from the lip on the bottom, which reaches almost all the way to the housing. As it is on the bottom of the battery, any obstruction I might place inside the phone must permit the bottom part of the battery to clear first.
I realized I was attacking the problem from the wrong angle. The battery isn't going upward (toward the camera) to lose contact, it is going outward - away from the body of the phone to lose contact. Even if it was going upward toward the camera, it would need wiggle room to do so.
I cut up a 1.5x1.5 chunk of thin cardboard (the kind from a cracker or cereal box will do just fine), and sealed it to the inside of the battery cover with masking tape.
It just fit. The battery door fit on cleanly, and upon multiple vigorous shakes of the phone, I couldn't even feel any motion.
Only issue I can picture myself running into is the fact that I'm selling this phone tomorrow morning. I think I'll have a hard time explaining this one to the customer
What ever happened to the good old days of well-fitting batteries in the 7290s?