Hello!

At home I have separated VLAN/subnet for TP-LINK network, details:
Network: 10.20.101.0/24
Gateway: 10.20.101.1
DNS: 10.20.101.1,8.8.8.8
DHCP has tested and good setup, serves IP, DNS and GW for clients (e.g.: raspberry, mobile).

I have 2 NVR:
UJNVR:        VIGI NVR1008H(UN) 2.20 (NON-POE)
            fw.ver.: 1.2.1 Build 241227 Rel.58554n   (Firmware is up-to-date.)
            Network setup (static IP):
            IP: 10.20.101.7
            Mask: 255.255.255.0
            Gateway: 10.20.101.1
            DNS: 10.20.101.1
            Attached CAM1,CAM3,CAM4,CAM5,CAM6 for recording.
    
TIBINVR:     VIGI NVR1008H-8P(UN) 1.0  (POE)
            fw.ver.: 1.1.1 Build 241205 Rel.68653n     (Firmware is up-to-date.)
            Network setup (static IP):
            IP: 10.20.101.10
            Mask: 255.255.255.0
            Gateway: 10.20.101.1
            DNS: 10.20.101.1
            Attached 3 RTSP stream for recording, but it is uninteresting in this story.
    
And 5 cameras:
CAM1: VIGI C340
CAM3: VIGI C340
CAM4: VIGI C340
CAM5: VIGI C340
CAM6: VIGI C340

All cameras has the latest firmware, and powered from the TIBINVR, but the recording is happening on the UJNVR (The TIBINVR is the 'honeypot' for robbers on my room, the UJNVR is hidden on the basement for recordings).
My issue is:
If I set my cameras IP to static IP (eg. CAM1: 10.20.101.11/24, gw: 10.20.101.1,dns:10.20.101.1) it is only remaining while the camera anyhow doesn't reconnect to his (UJNVR) recorder.
If I restart the UJNVR or the camera itself, the camera's gw and dns changing to 192.168.0.1.
If I set my camera's IP to Dynamic, then the camera gets IP, gw and DNS from the router, I see it for few second on the GUI, but a few minutes later it changes to Static IP.
And after the UJNVR restarts somehow, or the camera, then the network settings on the camera is changed to Static IP, the gateway and DNS is changed to 192.168.0.1.

The camera's unable to access the internet.
Why changing the DNS and GW on Static setting?
Why doesn't remain the Dynamic IP setting on the camera and changes to Static?