From 900mbps to 90 mbps @ 2 pm daily

Hello, I have fiber. Since August the speed fall to 90 mbps at 2pm. The technician installed a new terminal and a new gateway. I have replaced the gig network switch and redone the RJ 45 terminations to make sure the wiring was clean. I tried to disconnect extra devices and the issue keeps popping. If I reset both terminal and gateway late at night, it is back to 900mbps till 2pm then off I am on a conf call I lose sound for a few seconds get a warning about poor Internet connection. Speed is back down to 90 mbps for all devices. Resetting again the ONT and gateway does not restore the speed but if I reset the technical and the gateway after midnight, then it is good again till 2 pm. I am pulling my hair on the issue. I already had 3 visits from technicians and being an it professional I am not entirely novice either but this problem is above my networking skills. What could it be? I asked if Cox was throttling speed during peak hours, afternoon and evening. I was told no. Then I am out of ideas. I thought some device could have an IP conflict and I scanned my network for this and nothing conflicting pops up I checked the logs in my main computer not seeing any error or warning. I am really out of ideas as where to check for a problem. Cox confirmed multiple times that the signal to my home is very good. Any idea it suggestion as where to look at next? Many thanks.