I have a VTR and had a issue with it today dealing with a battery. I did a bad thing and drop it on carpet that was laid over concrete. It hit squarely on the bottom. It worked after that, but seemed to be down on power. The battery indicator was showing green, but I decided to charge the battery anyhow. When I removed the battery I notice the bottom negative post on the battery had a "dent" in the center of it.
The trap door has a small (about 1/8 inch) brass nipple in the center where it contacts the battery. I put a new battery in and it is as good as new.
Now to your problem:
Check and see if that small brass nipple is still on your trap door. It looks like it is just glued on. I don't see any indication of it being screwed on. If it has come off that could be your problem as the top spring does not contact the battery until the battery is inside the bottom about 3/32 and the door without the brass nipple is only 1/16 thick. This would not give good contact between the door and the battery if that nipple is missing.
Let us know what you find.