I wonder if a few batches of these sat somewhere cold and the adhesive holding the batteries let lose? If you were willing to take a minor risk, I bet you could run your thumbnail around the rear cover, pop it off and stick the battery back on the stickum. Of course, that would no doubt void your warranty -how they would ever know is beyond me...
OTOH, you've doubtless already voided your warranty by tilting or shaking your Glo!
