I have observed a simultaneaous drop off of the network of all my amcrest cameras POE and non POE connected to the same switch either directly or through an unmanaged network switch.
Nearly identical cameras from Dahua connected the same way do not drop. Cameras connected wirelessly through wireless network bridges do not drop. Amcrest Cameras connected through wires through a managed switch (ubiquiti AP secondary port) do not drop.
The ones which dropped are of 3 different amcrest models (IP2M-841B, IP3M-956E, IP3M-954E). All 5 drop at the same time when... I turn on my windows PC on also wired to the POE switch but via another unmanaged switch. When the drop happens, the camera becomes completely inaccessible and only hard power cycle recovers it. Not sure what is different with the amcrest specific firmware.