I recently purchased an Aston Power 4-battery charging hub for Evo Pro 2 batteries. It's doing a strange thing. When I initially insert all four batteries and plug it in, the center screen turns on, the fan kicks-in and the battery charging indicator flashes indicating (presumably) charging in progress. Then, after several minutes, the screen goes blank, the fan stops and the flashing ceases. The battery indicator on the batteries show some progress in charging but it doesn't appear to continue to charge. Any theories?