I recommend, I use it almost every day with my samsung galaxy note 4.
For those not aware: 2 click on the button once you have connected a camera
For the few small bubbles it's nothing, it not mean it not working.
Namely you can load the mains.
When loaded in blocks 4 small LED séteigne. When AC load and the charger is empty, the LED flashes one by one.
I post a photo