notPoE IP cameras with poe switch stopped working, what's going on?

Question

network hardware

What is available:
4 Chinese Misecu IPC-DM10C-2.0 cameras without PoE power supply.
1 PoE camera of unknown model.
Chinese PoE switch.
Problem:
Initially, 4 notPoE cameras were installed in a regular switch, and there were no problems for more than six months. In the future, we bought a PoE switch, rearranged all the cameras into it and added another PoE Ip camera. Everything worked for a month and a half. At the moment, the first camera stopped showing, after a week another one, and after a couple of weeks the third one. All failed cameras do not support PoE.
I tried to connect directly to the camera with an old / new cable, the result is no link. Food is all right.
PoE camera and one notPoe work, but temporarily moved them to another switch to avoid possible breakdowns.
What happened? Was the error in connecting notPoE cameras to the poe switch? What is the breakdown in the cameras, are the ports dead? Should the switch be replaced, or could it be something else?
Thanks for the answers)

Answer 1

Perhaps the voltage jumped on the switch and the cameras were not adapted to the load via PoE, they simply could not cope with it :)