Inability to upload any file

I often work with large files with audio and video that I need to upload to a personal webserver and a website soundcloud.com.  For the past year or so, these uploads never work, I am literally unable to upload anything over 1KB right now it seems.  This is also affecting opportunities to livestream or run video chat.  Everything related to uploading is lagging and not working.

I rarely upload anything greater than 4GB, most commonly I attempt to upload 1GB audio files. When I tether to my mobile phone using from another provider, everything works fine except for the fact that uploading takes 8 hours over the phone and should only take 15 min over Xfinity wifi.

I have worked with Xfinity Tech Support on the phone and on home appt.  I have tried 2 Xfinity Modems (the first one was bricked by xfinity support over the phone fwiw). I have attempted 7 computers, ethernet or wifi and still no ability to upload files via web browser or using scp from a unix terminal.  Using MacOS latest OS and earlier versions of Mac OS.

The tech support agent from Xfinity mentioned I may want to look into other providers. I don't have any other options in my area only Xfinity.  I believe this to be a more advanced issue that general Xfinity tech support would not be able to correct (i.e. DNS routing / load balancing issues).

I am happy to work with tech support and provide logs/traceroutes etc to help diagnose this issue. As of now I am only getting half of what I pay Xfinity for for internet.

Some observations:

1) I see timeouts happen regularly in traceroute as soon as the last 'comcast.net' server responds. 

2) soundcloud.com upload service simply errors out after hanging after some of the file has been transferred. I understand this you cannot support this and all I see is "it works or didn't" but it varies in when it fails, it generally never gets passed 50% before it fails.

3) Over scp to a personal webserver I get a client_loop disconnect error after some varying duration, it generally never gets passed 30% before it fails. Sometimes it immediately fails with 0% uploaded

client_loop: send disconnect: Broken pipe

lost connection

4) Is the IP assigned to me "red flagged"? 

Thank you