Well, it depends. Is it a Hikvision or some other generic brand?
I would think whoever did the initial setup didn't get something right.

There are so many variations we could be looking at here, it is impossible to really give any good advice. Would need to know the exact model number, what firmware it is on (that is becoming important these days, as different firmware versions can act very different too). What brand of IP cams. How these cameras are getting to the NVR (direct feed to the POE ports on the NVR or thru the common network using ONVIF).

Looking back at my replies from 6 months ago, maybe saying it was simple was incorrect. It's simple if the installation was done correctly, using modern equipment, paired with fully compatible cams.
Since we don't know if this guy is even using brand name equipment with North American firmware, let alone if anything has been installed correctly, I would pass on this job. Especially since it seems he's dragging this out 6+ months now?
Unless the customer is willing to pay for a complete install with possible new equipment. If it were me; for an 8 camera system, that would start at about $4K and go up from there depending if I had to re-run wiring as well. Anything short of that, I would walk from what I have understood.

You better believe any 'professional' CCTV company would do the same thing. Gut, replace, re-install. Which is why the guy is trying desperately to find a Ring Leader for his Circus, he doesn't want to pay.