ZMI Power Bank intermittently shuts down. How to fix?

Question

Batteries

I bought a Powerbank of this company a month ago and at the beginning everything was fine, but a week ago the charging started to play pranks. While charging a phone or other device, at an arbitrary moment it simply turns off and stops charging. Pressing the button on the case (turning on) does not give any sense. Only charging the bank itself helps in the problem, regardless of the duration, i.e. it is enough for a second to connect it to another bank and it again gives off a charge. Are there any solutions?