So I tried this with the wifi and had the same problem today. Speeds were perfect then as soon as I start streaming it drops to almost nothing. The I restarted the computer and it's back to normal.
So that shows it is not just an Ethernet issue and rules out faulty Ethernet ports on the Hub.
Can anyone help me with what is happening here?
Unless you get lucky and a fellow Lenovo laptop user who has experienced and fixed this issue stumbles across your post it is unlikely you will get an answer here. It is a device specific issue and clearly not a VM broadband issue.