Just to recap:
Your System:
Optiplex 7040 w/Intel i7-6700, 3.40Ghz, 16Gb ram, Windows 10 Pro ver. 1703, 64 bit
500Gb operating system drive & 4Tb WD Purple footage drive
HD hardware acceleration Yes (H.264)
BlueIris Build:?
Direct to disc
20 fps in the cameras
Cameras: 6ea. IPC-HDW5231R-Z
Switch: ProSAFE JGS516PE
Anti-Virus: Webroot
System Scheme: Modem/Router->Switch->Cameras
..................................|->BI/PC
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Changes:
Can you list the changes you have made up to this point? (this might be of use to others with a similar problems later)
Questions:
What BI build are you running? (I think I read you were up-to-date but not sure)
Have you checked to see if your
Optiplex 7040 BIOS and hardware drivers are up-to-date?
Have you checked to see if your
camera firmware is up-to-date?
Have you checked to see if your
switch firmware is up-to -date?
Have you changed your system scheme so that your BI/PC is also going through the switch?
Have any of the changes you have made, made any difference in your CPU/RAM usage (+/-)?
Suggestion:
Find a network analyzer (limited time free trial) and look at whats on your network and how much its costing you as far bandwidth.
SolarWinds is a creditable company and offer free trials if you sign up (Windows 10 or server (not affiliated). FYI, install and config is long and difficult! I will look for a simpler one when I get a chance.
Bandwidth Analyzer Pack
NetFlow Traffic Analyzer Overview