Always nice to see our online discourse healing in real time.
I'm not familiar with the Amplifi system but a quick look shows it has some QOS features to minimize "gaming" latency. I'm not sure how aggressive that is, maybe try turning it off?
Are you experiencing these slow downs over a wired connection? Lastly, you should be able to connect a computer directly to your cable modem and run some speed tests. That would give you an accurate idea of the current network performance.