slow gigablast speeds in las vegas

Wow....our problem appears to be the same. I am in Las Vegas, NV 89166. I noticed the dramatic drop in speeds on August 2nd. I called support on Monday, August 3rd, and a Tech was scheduled for the 6th for the hours I see a significant drop in speeds (3 PM-5 PM). Tech came out and said speed was good to my panel and left without checking modem or anything else and advised I had to troubleshoot my lines in the house for which I pay $10/month for them to solve. I subsequently took my new modem, Motorola M8600 (I swapped from Netgear CM1000 on August 3rd), and tested outside my house at the panel connecting to the line coming from the street. Guess what.... same speed as in my house with two different DOCSIS 3.1 modems (45 down 34 up). I called support and requested a supervisor since I was very unhappy with the Technician's (Christopher) performance. The supervisor looked at modem signals remotely and confirmed signals were significantly outside the acceptable range. The supervisor agreed the previous Tech (Christopher) incorrectly diagnosed the lines/connection in my residence as the problem. Subsequently, a second Technician scheduled for Saturday, August 8th between (3 PM-5 PM). The Tech (AL...) tested the tap at the sidewalk using his modem and my modem. The best speed we saw 120 Mbps down and 34 up) The techs modem and my modem had nearly identical results at the sidewalk. The Technician then tried a different port on the tap at the sidewalk. Same results. The Tech (Al....) concluded the problem is not in my house nor was it my modem. The Tech said he was writing up the problem for maintenance. He stated that it was a problem beyond his level to resolve. On Tuesday, August 11th, I again called Tech support to check on the status of my speeds since there had been no change in my slow speeds (30-40 Mbps down and 8-17 Mbps up). The first support rep stated the maintenance ticket was closed and maintenance commented "unable to duplicate." At no time did I see any improvement from the time the second tech came on Saturday and Tuesday's support call. I am not sure why the maintenance person was unable to duplicate... I am assuming they checked at 6 AM and not 3-5 PM. Maybe because the maintenance person is incompetent or never actually did anything because they know the underlying problem is saturation/congestion (too many users on my node). Since my problem had not changes the phone support said she would be transferring me to maintenance. So I had a lengthy wait for maintenance support and instead, I was connected to remote computer support. He said he had to transfer me to another support person that he is not the support I needed. Again another lengthy wait for the next support person who advised me he was scheduling another tech support person in maintenance to look into the problem (08/15/2020, 8-10 AM). I then readvised the phone support the problem is worst between 3 PM to 6 AM. He subsequently rescheduled for after 3 PM and after speaking to 4 phone support people, and 1 hour and 45 minutes later I concluded my third call for this problem. So here I am and it is Thursday, August 13th and I am still suffering the same speed degradation. The best speeds are in the morning hours between 6-10 AM where my speed is 220-380 Mbps down and 15-35 Mbps up. Just another note.... I have had Gigablast since its initial roll out about 3 years ago. My speeds have been very good speed. However, in July 2019 I had a week where speeds were really bad and again it had to be sent to maintenance who resolved it. Unfortunately, not this time. I suspect Melissa Martin may be correct and Cox has oversold Gigablast in the Las Vegas Valley.