[SOLVED] Problem to power multiple devices with a powerbank

My powerbank is connected to UNO via its 5.0V/GND pins which manage display, sonic sensor, pad and led. All work fine.

In paralel this battery can power another microcontroller via its 5.0V/GND pins too but I noticed 2 problems:

  1. If the second microcontroller is an Uno, Mega or Pro Micro (5V) that's ok, but when I try with an ATtiny85 (Digispark) or a Nano (5V) it's like if there's not enough power... Nothing start, leds indicator are very dark. However my powerbank can deliver 2A. Thats strange!

  2. When I unplug the 2nd device in parallel (it could be just a led, not necesseray a microcontroller), the first microcontroller resets. It's like if the powerbank restarts when it detects a variation of current. An idea?

It would help if you posted a link to the power bank that gives technical information. There are a lot of different varieties.

The problem was from the type of wire I used to connected boards between them: a jack cable with 4 poles does many bad contacts during the connexion (before it becomes stable inside). Shortcuts certainly made reboot the all...