I had to test that memory card ejecting by itself situation and had hard time to reproduce it (pcb revH). Then took my second mooshimeter (revJ) and card popped out when i just opened the thing.
Only difference i could find was maybe just under half a millimeter difference in card holder placement. I have to wiggle back cover a little to get it past memory cards edge. Strange. Maybe i have not had to open my newer meter after i put that memory card in to it and just got lucky when closing the whole thing first time.
Battery contacts had a problem in early mooshimeters, when there was sharp burrs that could break the battery wrap and positive battery shell would get into contact with negative battery holder. If this is the case, you could (and should) dull those with just about any tool that would feel right in your hand. I got even more paranoid and wrapped sides of those battery holders with kapton tape.
More about battery contacts can be found here: