Loosing internet connectivity and slow speeds

I am having trouble with my gigabit connection. First of all I never get full gigabit speeds even when hardwired to the modem. I get full speed during off hours sometime when I am lucky. Secondly I keep loosing internet quite a few times every day (Get kicked off from meetings and lose file transfers). I had three techs come in to troubleshoot.

First tech simply hooked up his meter and saw full gigabit speed and was not ready to accept that there is a problem and simply left.

Second tech was very reasonable and saw that the downstream signal levels were too high so he inserted a 6db attenuator pad in the line and also he noticed a lot of couplers near the outside tap where the line drops underground and wired the cable directly to the tap. The speed was good but he noticed a lot of noise in the line so he opened a request to replace the cable that goes into the house.

The third tech that came to replace tha cable simply refused to replace the cable and was not ready to accept that there is a real problem. He replaced the 6db attenuator pad with a 4 way splitter and capped off the unused ends. This changed nothing and worked same as the 6db pad. I am still however getting a lot of disconnections trhoughout the day. I have changed a couple modems and my wifi router but nothing seems to help. I see a lot of uncorrectable errors on all downstream channels and have to reboot the modem everyday. Not sure how can I get comcast to swap the underground cable drop to my house.