You're onto something here.
	
		
	
	
		
		
			I watched a camera on the webUI and it does not seem to go down so I am thinking it is NVR related,
		
		
	 
Q1: Plz confirm you surfed into the cam's webUI, and didn't view the cam through the nvr webUI.  I suspect you surfed to the cam directly, but I want to  make sure.
Another test, set your NVR for continuous recording (as vs "record on event")  Later, check playback.
Q2:  Are there gaps?
A2: If "no gaps", then your cam network (at least) is remaining up, the cams video reaches the NVR, and video is getting recorded.
Meaning your NVR is dropping off a functioning network.
Meaning an ip conflict of the NVR's ip addr may be the culprit, as you suspected.
A2: If "there are gaps", run the continuous ping test on one of the cams.  Does it drop off when the NVR goes dark?  What does log fille say?
Q3: Check the  log file on the NVR.  From NVR webUI screen (which is handy for me right now), it's under: INFO, LOG.  On the nvr native UI screen, it's something similar.  Check the log file for items at the timestamp of when the NVR disappeared. What was logged?
Q4:
	
		
	
	
		
		
			Please confirm your cams and NVR are wired (and not WiFi)
		
		
	 
When I view my NVR using a wifi connected laptop, I  lose cams when the microwave oven fires up.  All cams are wired, it's just my laptop wifi link to the cam/nvr subnet that is affected.
Q5:
	
		
	
	
		
		
			Did your network have any recent changes?
		
		
	 
Let's leave no stone unturned....
Q6: 
You say it's happening more frequently 
today.  Any hunches why?  
- Is the nvr in a really hot room, and today was warmer than usual?  
- Lotta lan activity (netflix, music, file transfers, etc)
Fastb