I'm experiencing failing shots when I'm using a battery other than the original Epson, but only when the battery indicator tells me the battery is 1/4 full or less. It seems the Epson battery is better able to handle the fluctuations in power consumption than these other batteries I have. Symptoms are very clear: indicator tells me the battery has juice, I shoot and the shutter sticks refusing to budge at all. Problem is easily solved by switching off the camera, removing the battery and replacing it again, switching on the camera and (trick of all tricks) switching shutter speeds. That releases the shutter. I'm happy to have 3(!) batteries at hand, of which 2 are not Epson originals. These two extra batteries are my fall back batteries, and I use them only when the Espon is really empty during shooting. Otherwise I recharge the Espon battery before going out.
I don't know if this is what you experience but use this info for what it's worth. 😛