If you want to run 2 slices and full frame rates, you will need over 1.6mb/sec and up to 2mb/sec uploading from the radio.
However, you can slim it down a lot by reducing your frame rate and only using 1 slice to under 300kb/sec.
In this example, which I just grabbed from my remote, it shows it hovering just under 300kb/sec and I have a very acceptable panadapter and waterfall on 1 slice listening to 80m SSB.
More import that speed is latency and you can see from the 2nd graph that I am hovering about 50ms.
This is pinging the firewall at the radio end from the Maestro end. The vertical red lines are actual ping failures which I might or might not have heard on the radio.
You might want to try by running pingplotter to some site local to your ISP, maybe their web page and see if you get a consistent link/ping to them. Pinging isn't the best tool, but it is one of the only ones we have for long term monitoring. That is what I did the above graph with.
What I think you are going to find is that there is some latency going on and that is impacting things.
73 Martin AA6E
Another area to check out is Buffer Bloat. Check out this thread: https://community.flexradio.com/flexradio/topics/minimum-speeds-needed-for-remote-vpn-and-wan-upload... There is some troubleshooting information in the thread. I moved to the IQrouter, and while your mileage may vary, it solved my Maestro drop out problem. I'm running DSL, 12 down, 1.5 up.
After my contract expired, I figured; let me try Xfinity/Comcast who was offering fiber to the house with much higher speeds at a lower price than AT&T.
I took their offer and I must say; I wished I could had done it earlier.