Upload speed dropping and inconsistent at random intervals, for over 3 years now.

Hi. I have been dealing with this issue since at LEAST,  2023. I need to find a long term solution, as multiple people on my house run live streams, and this affects our ability to stream to twitch, which is part of our income. My download speeds, usually,  are greatUsually more than I am provisioned for.. however,  my UPLOAD speeds, which I need more than download, will drop to almost nothing at random times of the year. the while, download speeds are fine. I say times of year because this is not a consistent issue there will be months out of the year my service is great, download and upload, but then this problem comes back, without warning. Sometimes this issue clears up later in the day, which coincides eith the fact that usually when I reach out to customer service about this, im told there is maintenance or upgrades happening in the area, but never for how long or when. But it will happen for weeks at a time, and during this, my upload speed will be unstable to a point it makes livestreaming to twitch almost impossible, due to the fluctuations in speed, from like 0 to 25 to 35 and back. 

I've had a tech come out as far back as 2023 and when they did,  I was told there is bad noise to signal ratio on the line we use for internet. So. That in mind, I was told the only suggestion they had was to replace the line, except,  xfinity doesn't wall fish anymore, so they wanted to drill into my house from outside the wall, my complex said no. Which at this point would force me to call out an electrician or private entity as the other wallplates in our house are in locations that make using a hardwired connection impractical and well, we need ethernet. 

Thats where the twist to this issue comes up. Once I started looking into Electricians in my area, Vancouver Washington,  the problem suddenly went away without explanation. Everything normal and functional. Which tells me, my noisy coax cable is not the primary this problem exists,  if its the cause at all. On top of how only upload is affected, id imagine my download would also be affected...

But I need help. I need to find a solution or get in touch with someone who can. Customer service doesn't seem to understand my problem,  and techs suggest I need to replace the line in my wall, but they cannot help me because xfinity doesn't do that anymore.  This leaves me subject random intervals of interruption to a portion of my income, throughout the year. This also affects my sister more than myself because it tends to happen more during daytime hours and we now have a routine of having to run speed tests before considering running live streams.. and it all feels unnecessarily stressful, especially because i have no idea what's causing this.

Id also like to add, i build computers and have built all the pc's we use in my house, so I have tried every form of troubleshooting known to man that I am able to perform on my end. And no, restarting my modem doesn't fix my upload speeds at all.