Daily Disconnects and Speed Fluctuations

I have been having an issue with internet for some time now, and now it's getting very frustrating, here is what's happening.

I started noticing some internet connection drops/disconnects in which I would lose internet access for about a minute and then it would come back on. This started occuring while I using a Cisco DPC3825 Modem and an Asus RT-66U Router. After noticing these disconnects I contacted Cox and they promptly sent out a technician to find the cause. The tech that showed up looked through the lines and removed some unnecesary slpitters and changed some connectors as well as adding some filters on the line going in to the modem which he said were needed, as the signal needed to be filtered because there was nothing else hooked up to the cable line (TV's or set top boxes). I was told this should fix the issue and they were on their way.

I continued using the internet for the next few days and noticed that the issue was still happening and called cox tech support which sent out a second tech to find out what was going on. The tech that came said that the problem was the modem ( Cisco DPC3825) because it was an older one and they have had issues with the modem and recommended I purchase a new modem and also upghrade to a  faster modem (16x4). So, I took his advice and purchased an Arris 6183 (16x4) and while I was at it also purchased an Ubiquiti Amplifi Router to replace the other router (and eliminate the possibility of a bad router). I hooked up everything and was amazed when the speed tests showed 180-190Mbps! I thought replacing both the cable modem and router had finally solved the disconnect and spped issues as well as increased the speeds. However, this was not the case. 

Soon, I started noticing the disconnects and speed fluctuations again and had to resort to calling cox again. They did the usual reboot the modem over the phone as well as clear the cache/reset the modem when I called on several occasions which did help regain the speeds and connection but they had to send out a third tech. On the day the third tech came, I was on my way home to meet the tech and he called my phone and told me he had arrived and I told him I was less than 5 minutes away and would meet him shortly. When I arrived to the house less than 5 minutes later I saw him in front of the house and he said "I just finished, and your internet is fixed" I thought wow, that is incredible, I have never seen someone fix something so fast without asking the customer what the issue is. He then told me that the reason I had no internet is because I was hooked up to someone else house/line and that he hooked me up to the right line. I told him that wasn't the issue I was having or called about and that I did have an internet connection but had issues with disconnects and speed fluctuations. So finally he came inside and checked to see that the modem was on and connected and he said it's fine and left. 

This did not fix anything and I still had to deal with the same issues with disconnects and speed fluctuations. Normally after a reboot on the modem I get about 180-190Mbps but when it fluctuates, I get less than 20Mbps. This is unacceptable, not to mention the interruptions in service which put my devices offlline (Cameras, Home Automation, Nest Thermostat, Nest Smoke Alarms, Home server and other devices which I use daily)

Today (9/27/16) a fourth technician came out to try to fix my problems. A few minutes prior to him arriving, I did a speedtest (speedtest.net) and it clearly showed speeds around 10Mbps and showed him the results as proof that the speeds fluctuate greatly. He checked the lines, connectors, signal, etc and said everything looked good and there was nothing abnormal showing up and the speeds were good (of course, because the modem had just been reset while he was here) He stated there was not any visible issues at the moment and that it was probably my router (Ubiquiti Amplifi) which I just bought and installed earlier this month since I was having the same issues with the other router. So he said I should connect my modem directly to my computer and see if I still have the disconnects and speed fluctuations. 

And so, here I am directly connected to the modem with my PC trying to rule out the (Ubiquiti Amplifi) router as the cause. I am highly doubtful as I have replaced everything regarding networking with the same results in the end. I want to add that one cox tech on the phone suggested a Uninterruptible Power Supply to ensure it wasn't an electrical power surge causing my modem to get kicked offline for a second. Well, even though it was a long shot, I bought an APC UPS and the issue persists.

I am very frustrated at this point and have not had a reliable internet connection for some time now. I get told different things from everyone I talk to for support over the phone or technicians who come out and nothing has solved my issue.