Like Mike,
We've seen this issue, and in 100% of all cases it was transport related. That includes updates applied to a server, that resulted in the LAN drivers having an issue. I can't find some screen captures we've taken in the past, but the symptom is more a horizontal tearing that is recorded in the video. With every new server, or a server we are responsible for, and at any chance we are getting the latest LAN drivers from BC or Intel.
We've also seen where a client had two NICS, each with an IP and gateway on the same subnet...
I would start by looking at the Totalbytes received using performance monitor. We've ran the Dell OEM 7xx and 5xx servers up to 35Mbytes/sec for almost a year before adding another server.
Never let a user view video on the server console monitor.
LAN drivers are equally important on a multi-monitor viewer (quad 30' in @ 2550 x 1600) for example... Older XP machines (disable hardware excel) (viewing only issues of course)
To better isolate the issue, crank up a handful of cameras to the best settings and highest frame rates..
We've tested this with 6 7K cameras, all set to MAX, plus many more... running a 1G segment up to near 50%, and over 500mbits into a server... after that we started having record issues... Duh...
Avigilon has decent disk bandwidth tool that will saturate . test the disk subsystem. You might have a failing disk or under performing disk.... Tech support can collect the data....
Happy to comment privately, or share some tools...