Repeatedly slow upload speeds

Greetings all, 

I am on the Preferred tier and have been for three plus years. Up until two months ago, I have had no issues. And then my upload speeds slow diminished. I worked with an representative whom sent out a technician to investigate. It turns out the technician found an issue with the service node and a new technician was dispatched. After several days and several calls, I found that the second technician found the home run to the service node needed replaced. And after that dispatch, I seen no heard from no one at Cox. After a call in, I found out that the only notes on the case was that the service was "fixed". 

And for a couple months, all was well. But again, in the last few days, the same issue surfaced. I went ahead and replaced my modem with a recommended modem. It seemed to help a bit, but the speeds bounced around and then finally bottomed out at around 1.2 to 1.3 Mbps. 

I get my advertised download speeds, but I am far from my upload speeds. And, I have tracked my history on speed tests and I hold a solid 5 to 6 Mbps when it working correctly. When it fails, it runs down to .5 to 1.3 Mpbs. 

And as a note, I have performed the following:

1. Factory reset on router

2. Removed router and plugged into the modem

3. Reset modem

4. Replaced modem

I am using Speedtest.net as recommended by the Cox technician and I am using the Cox speed test in their network. And even in their network my speeds are reported slow. It is not constant, and that is the frustrating part as I cannot get a low speed when the support reps review the speeds. 

Does anyone have any solutions?