I feel like I'm having the exact same issues. Only upload speeds are affected. Not download. I've had Cox replace cable modem and no bueno. Not sure what's going on. I'd leave but I can't no competition here where I live in Macon, GA. Sad that we are both having the same exact problem and 1/2 a county apart.
_I_ believe the issues is QoS or traffic shaping by the ISP to handle over provisioning. XD
https://imgur.com/a/EIBNKNW
But yeah... so frustrating. I can replicate it super easy to. Just doing test uploads and after 3mins... the throttling happens where it goes down to 0mbs instead of the normal 10mbs upload. So sad. :( So frustrating. GL to you OP!
