Maybe the cameras were broken on purpose.
It were a co-inky-dink, I am sure.
Like maybe someone disconnected the feed wires to these cameras for a couple seconds and using a small capacitor sent a 1000 volt signal down that wire to the camera burning out the circuit board in the camera.
The saboteur reconnects the camera feed before anyone comes to check out the failed camera and no one is the wiser.
Looks like a bad circuit board. Pretty common and not too suspicious.