That sounds like it could be a bug or quirk in how Dahua's software / NVR is designed. Have you asked their support? It would be good to know what their take is on that.
Pro Focus LLC | 07/06/16 12:56pm
I think the issue is that Dahua NVRs will always fill the lowest numbered channel first. So, when you unplugged ch15 and then plugged in ch16, it bumped it down to fill the void of ch15. You can simply try to do the reverse now. Unplug both ch15 & ch16, then plug in ch15 first. Then plug in ch16 after that. This should rearrange them for you.
Worst case, unplug all channels, default the NVR, then plug them back in to the NVR in the preferred order.
Yes i spoke to tech assist and really i should have not messed around with those cams on channels 1 -16 and added switch to other network port .So on the on board switch 1-16p just add until full, cams will be addressed 192.168.3.65 to 81 then other 16 on 192.168.2.30 to 46 something like that.
Unfortunately on Dahua products, once you connect a camera to the system it will retain its position on the screen even if you connect it to a different POE port. The only way to get the camera back to the position you desire, would be to disconnect all cameras and load defaults on camera settings. You do not need to default the entire system, just the camera settings. (Main Menu-System-Default: Check only "Camera" click apply.
When reconnecting your cameras, no matter what port you connect the camera, the channel assignments are determined by the order the cameras are connected to the system.
Hope this helps.