HeKa

Hi, About 10months ago I installed NVR and 10 IP-cameras to my friends little cargo terminal. Im not professional with CCTV but im able to install these. There is 9 dome/bullet cams and 1PTZ. I used 2x 8port POE switches and from there ethernet cable to NVR. All worked well for 10months but now suddenly one day cameras begin to go disconnected. All of the cameras go disconnected and then it can come back in minute or 15minute. All other cams are connecting and disconnecting except PTZ which is always offline. notice differnece between disconnected and offline. Sometimes some cameras stay disconnected hours. if i unplug wires from switches and put back i think that seems helping it and most of the cams come live after that but sooner or later they are continuing that connecting and disconnecting thing. I decided to change NVR and see if that makes difference. a few hours all cameras came back live but then all begun again. After that i changed both POE switches too but no difference. Some times it shows all but 1 or 2 cameras for hours and then suddenly only like 4 cams are live for next hours. With CCTV tester i can connect to all cameras except PTZ. Now im wondering is it possible that if 1 camera is broken it could cause all this? Only thing i know they have did before all these problems is that they increased their internet bandwitdh/speed. They havent installed anything in the building so wires etc are all same way they were after installation.