On Gigiblast speed drops from 760Mbs on PC ethernet connected to 7-10Mbs after maybe a days use until reboot than high-speed returns?

Thanks - I have been up about 3 days without rebooting and I just tested on speedtest.net and the site you recommended https://www.cox.com/residential/support/internet/speedtest.html

Both were very close 63Mbs down and 64Mbs. Upload is always the expected about 35Mbs since not on fiber.  As indicated if the reboot will go back up to about 700Mbs range. This is hardwired ethernet to the router on high end chip etc PC.   Have CM1000 DOCSS 3.1 modem and latest Orbi MAZE router. 

For most of what I am doing really don't notice slowing speed unless it gets down to about 10Mbs - but nice to have close to the gigabit I am paying for.

Just for fun, I redid the PC connection direct to the modem. Detected but no internet access so rebooted modem. OK, still same 68.6Mbs down direct to the modem, bypassing Router (and Gigabit switch I have since so many connections to devices.) But that should eliminate any issue with router etc yet still slow DL. Ping 10ms which seems fine.

MB is ASUS PRIME Z370-A
I did some Googling and didn't find any reports similar to mine with the MB. Since it starts out at about 700 but deteriorates over time is weird :( and frustrating!  MB is rated for gigabytes

I have 32GB of fast memory about 48% in use - 37% of used is Chrome since I understand does a poor job of releasing. Only have four tabs open in Chrome.

Anything else I can check :(

What irony  - I just tried rebooting everything and had the modem kept rebooting and not locking in until about the 4th dry.  Now back up and DL is 750Mbs but will monitor it over the next few days.  

Oddly enough a week or so ago a major Phoenix outage when I was replacing TIVO and was going crazy not being able to get it to work (On MOCA) till found out there was an outage. 

I rarely use a smartphone unless traveling... but think there is an outage map via web will look for.  I am used to my five 28" monitors in front of me plus a TV and a big keyboard and mouse vs phones!

Found the internet map with huge outage area.  Interestingly my Internet and VOIP phone work but the icon in the tray says no internet access yet I obviously have since sent this. Modem light all normal.