Originally Posted by LoneStar
I just received mine today and made sure it worked but haven't swapped batteries yet.
If you have the same trouble, I think it is solved by pulling out the battery contact strip in the corner of the battery compartment (the one that connects the two batteries in series) and putting a blob of solder on the contact point of the bottom-most battery's + terminal. (I also used a needle-nose plier to pull the contact spring of the other battery's + terminal, but this didn't solve the problem - I think the bottom battery was probably the only one that wasn't making contact. There are some plastic bits in the compartment that could also be ground down to let the battery slide further and make contact - perhaps these could be dremeled away a bit.)
Here's the battery variance culprit, chinese battery on left, Duracell on right: