Out of interest, which drives do you have in your NAS, how many of them?
Also, is your Unifi switch on it's latest firmware? Is the Edgeswitch on it's latest firmware?
yes if you can try without the CCTV recording to the NAS.
Although it might only be writing @ 2.5MB/s, if you are trying to read from it at the same time you are forcing the hard drive(s) to constantly seek to two different locations (which will cripple read speed)
Worth doing a large file test with the NAS on the same switch (with the CCTV disconnected).
Note speed.
Connect up CCTV
Note speed.
Disconnect CCTV, move to other switch.
Note speed.
Connect CCTV.
Note speed
If it's just 2.5MB/s from the CCTV, then it shouldn't impact your normal copying speed much.
Do you know if its easy update. My Unifi ACPro does it automatically but I've not found a Click here to update yet on the switches.Ubiquiti update firmware very often. Update them both.
What version is your controller on? It should be 5.4.11, this will give you the latest updates for the Unifi gear.
Not sure what you mean by your GPU playing up. Whatever it is, sounds like something was running at 100Mbit.