I don't think it is a cable issue. Possibly I'm not understanding, but I have no issues at the monitor attached to the nvr, just on a networked computer. I also seem to be ok using the iphone app, with both LAN connection to cams and outside ddns address.
BTW, where can I get firmware v3.4.0 for the nvr? I've only seen the one I'm currently using as the most recent.
All h.264 with no option to change it. I can't see why it would be a bandwidth issue. I have no problems streaming or anything else that I can see.
Do not put v3.4.0 on... v3.4.2 (v3.4.0 was another Hikvision disaster!)
When you say no issues on the monitor, are they all main stream or sub-stream? And are all the seconds ticking, sometimes the image will freeze.
It sounds more and more like cable issue. It doesn't take much time to take one indoors and connect to a shorter made up patch cable to eliminate the issue.