Incoming network packets cannot be received by correct LAN port causing disconnect issue (camera or server) or recording lost issue.
NVR with dual LAN ports provided, the main purpose is to separate the network environment into two parts - one is for Local Area Network (LAN) access with cameras, and another one is for Wide Area Network (WAN) access to the Internet. The dual LAN ports architecture is not for the purposes of increasing network throughput (link aggregation), doing load balance, or for network redundancy. So, if clients setup both LAN ports to the same subnet, it might result in the network packets lost because the network packets might be sent to the incorrect route.
For example, as shown in below routing table, this is a WRONG routing table setup by the users. Both LAN ports (eth0 and eth1) are setup to be as 192.168.0.x/24. So, the NVR routing table would look like the result shown in below figure.
For routing table mechanism, it will try to match the IP prefix (in the packet that is about to send out from the NVR.) in bits format as many as possible with the "Destination" IP address shown in the routing table list (started from top to the bottom) to decide on which route the packet would be sent through. Due to the Destination IP addresses for dual LAN ports is the same in the NVR routing table, the LAN2 interface (eth1) would be chosen always to forward all the network packets out from the NVR.
So, if the network packets from LAN1 (eth0) are about to send out, it will go through LAN2 (eth1) and reached the destination IP address device. And if there is any responding network packets would be generated by the destination IP address device, those network packets would be received by LAN2 (eth1) even they've been expecting by LAN1 (eth0). For those tasks in NVR waiting for any responding network packets via LAN1 (eth0). Then the connection would be lost since the responding network packets cannot be received by LAN1 (eth0) anymore.
To avoid this situation, please change the both LAN ports to different network subnet then see if this issue is still remains or not. Please see an example shown below.