Intermitent and Variable Upload Speed for the past 6 months.

For the past 6 months I have had extremely intermittent upload speed. Randomly but at least 2-3 days a week my speeds will start bouncing all over the place and sometimes even sit aroun .5-2 when it should be 30. I have the 300 down 30 up plan. This happens on 2 separate wires dwsktops. When this happens the download speed is usually effected as well but only in extreme cases is it noticible for download. This will last anywhere from 1-8 hours. I need a constant steady upload speed for my job so this has made it gety inconvenient to work.

To this date I have had 13 tech home visits, replaced the Ethernet cables going to the computers, replaced the modem/router provided by cox 5 times, upgraded my internet speed and data limit, and none of this has changed a thing.

Is this possibley a plant problem or an issue with the line somewhere out on the road. All the techs have been able to tell me is that there is interference in the line somewhere but they do not know where.

This has been an absolute nightmare with no end in sight. Does anyone have any thiughts? I have another field supervisor comin out this week.