I've been experiencing a very slow upload speed for a couple of weeks.
I also upgraded from Performance to Extreme Pro a week ago.
Download speed is limited to 300Mbps, which is understandable since I'm still on my old DOCSIS 3.0 modem.
But my upload speed is a measly 1 Mbps. I can't do any video-call, let alone gaming.
I've been on chats or phone calls many times with the agent, and what they can do is just restart the modem or do "troubleshooting" on their side. I've also power-cycled, plug-unplug the cable from the wall, and other basic troubleshooting.
Here's the modem status page https://imgur.com/a/yWxUsFa
FWIW. The upstream / return path "pipe" is much smaller than the downstream / forward path pipe is, so it is more easily saturated.