Common steps to isolate field problems
Change a computer
This is always the first step that can effectively rule out many environment factors. Try not to blame the software first because no software can run perfectly in all combination of all computer components.
Read over the Internet about some diagnostic techniques
Rebuild the whole system
If the system starts good, and became bad later, then it could be something or someone has tampered the system. It could be a good idea to rebuild the whole system from scratch to rule out tampering factors.
Recording disks - periodic health check or replace
Hard disks are known to wear-out after prolonged usage. Building an NVR server with old disks is particularly risky because old disks may contains bad-sectors that may lead to data corruption. Some disks are equipped with self-repair function that automatically moves data from bad-sectors to good-sectors so it does not show damages in an obvious way, but the self-repairing mechanism takes time, and therefore reduces the overall bandwidth. The read-write-heads of a damaged disk could also cause the disk to become much slower.
To reduce this risk, you should periodically engage maintenance to your NVR system by measuring disk performances. If the performance is degraded since last measurement, it could mean a danger signal that the disk is about to be irreversibly damaged.
Examine network bandwidth
There are many readily available tools on the Internet that help you to do that. Example includes "iperf" and "NetMeter". It can give you the objective view of how much bandwidth you are giving into the NVR.
SafeMode is a NVR software feature that provide an alternative software startup sequence with certain functions disabled. Please refer to user's manual for more details.
Read-through all technical documentation
Genius Vision NVR is a highly sophisticated professional software. It's possible the information you need is simply buried somewhere inside the product documentation. Most of the time, a user who isn't familiar with the software could be responsible for messing up a working system due to user errors, so it's really a good idea to get familiar with the software by reading through all its documentation.