vscience

[I use the latest ESET Internet Security version] A while back I started to notice my single thread speeds were going slow when I did speed tests, also downloads were going slow. It seemed quite random, a lot of the time it would be fine for the first few minutes of starting up my PC and then would slow down from my maximum 60mbits to approx 20mbits. I could always get full speed back for a minute or two by disabling the network adaptor and then re-enabling it. I couldn't work out what was causing it, I blamed it on my motherboard or NICs or router. Then my motherboard broke and I assumed it was just a symptom of that, even though I had tried two USB3 to NIC adapters and a new NIC card and different chipsets (Intel, Atheros, and Realtek), and the slowness happened with them all too (but as they all plugged in to the motherboard in one fashion or another I just assumed it was the board).
So anyway, I got my new Ryzen PC yesterday, I noticed after re-installing everything the same happened again, so it HAD to be software as it was a brand new PC, so sadly I wasted a lot of money on NIC cards/adapters. So this time I reset Windows again to start fresh, and I made a note of every item I installed and when the problem begins, so I would install new software, speed test, and wait half an hour and speed test again. Everything was fine, until approx 1 hour after installing ESET, then the problem happened again. I uninstalled ESET just now and the full speed is back. Now, I can't be 100% it is ESET, because it did used to be random, but I have done speed tests 20x since uninstalling ESET and it has been fine again which is very unusual. Normally even though it was random, once it had begun going slow only enabling and disabling the adapter would help, or resetting the PC, in the very short term (a minute or two). 
If curious I use Interactive mode so I allow most things through, occasionally I deny but very rare only if I am unsure of the software I have downloaded.   
I probably should have fiddled with other settings before uninstalling, but I was eager to see if it was ESET or not as there had to be a common link with my previous computer, which was software of some kind. Now comes the odder bit. My other older PC (not the broken one, I always run 2 working PCs at home) also uses ESET, and that is fine and always runs at full 60mbit on single thread, so I have no idea why this is happening to this PC, unless there is some software I use on this PC that I don't have on my other one that somehow conflicts with ESET. The only similar left overs from my previous PC that broke that also suffered this speed issue is my PSU, case, Radeon graphics card, my RAID card, 6 external HDDs, 4 internal HDDs. The main OS drive is totally different. While I had the speed issues I removed my RAID card, my USB3 card, and all HDDs except the M2 and still had the issue, so I deduced it can't be any of those hardware items causing this. 
So, assuming this is ESET, I have to then think what is not on my other PC, which runs fine with ESET. So we have the AMD graphics card (a RX560), my other PC uses Nvidia. A different chipset, both my broken PC and new one is a Gigabyte model, although totally different model of course as my last CPU was an intel i7 and my new one is a Ryzen 2600x. The PSU. Software wise, I guess the chipset drivers would be different, the graphics drivers would be different, the motherboard software would be different. I keep both PCs very similar in the other software installed, as they are desktop PCs so I keep them fairly similar so I can use the same software in different rooms on big monitors. 
So any ideas ? Sorry for no log, as I uninstalled, but I am just curious if you have heard of this single speed issue happening before. Speed tests are fine for multi-thread tests, it is the tbbx1 speeds that are slow, but that seems to effect downloads too. I also don't get why disabling and re-enabling my network adaptor seems to fix the speed for a minute or two. So if you have heard of this issue before, please let me know, if not then I guess I will just keep using ESET on my other PC and just keep to Windows Defender on this one.
Thanks. Knowing my luck, I will post this, and then find speeds are slowed again and it won't be ESET, but it seems too much of a coincidence that it went slow shortly after installing and better again after uninstalling.