Losing internet connection every few minutes

My connection is losing internet every few minutes. I'm having this issue for more than 5 months now.  I had multiple tech visits (like 5-6 in the past five months);

In the beginning, I had my own modem (ARRIS SB6190- DOCSIS 3.0). Tech complained that it's the modem's fault. Even though the modem log shows several T3 time-out errors, they told me it is the modem because it is owned by me. So, I changed the modem to a MOTOROLA MB8600 DOCSIS 3.1. then again, logs had the same T3 issue.  And the drop continued. Then again, the tech complained that it's the modem, and since I'm not using a Comcast modem, they cannot do anything.

Then I replaced the modem to the latest Comcast XB7 modem in September; drop continued like before after that had two tech visits and they blamed the building and told that cable issue with the building, and last month they replaced the cable from the modem to the building node with the newest cable.

Basically, now all the equipment from the modem to the end of the building is changed and using the newest ones, and still, it is dropping the connection every few minutes.

The biggest frustration is It is dropping all zoom calls, video streams, websites, anything and making working from home a horrible experience.

Previously it was losing connection for about 30 seconds. Past few weeks, I sometimes notice it lose the connection for more than 5 minutes.  Somedays, it does not drop at all. Somedays it drops every few minutes.

I'm using a LAN connection from XB7 to a PC, and I'm using a WIFIconnection to another PC, both PCs losing connections same time. 

After I got the XB7 cannot see many details in the logs like the Motorola or Arris probably hidden from consumers in XB7. 

I saw several threads like this in the Comcast forum.  but non of them seems to have indicated any solution.

any help appreciated. Thank you.