I have a Canon 5D Mark ii. It has no problem when I use it with the stock LP-E6 battery. But recently I got a dummy LP-E6 battery box that can connect to external USB-C charger. When I use the dummy battery, the empty battery sign always blinking and the camera can not function. However, if I open the battery cover and close it, all function well. It seems everytime I turn on the camera power switch or USB-C charger, I need to open and close the battery door to “activate” it. A bit annoying but it does work in this week. I could not explain why though. just to share.