I solved the problem for my Surface Pro 4 (SP4) which (also uses the Marvel Wi-Fi chips) through the 'Security' submenu (under 'Wireless' on the Hub 5 menu to the left of the screen). After long-winded attempts to use VM support with no result other than a referral to the Device Repair Service - with the (turned out to be false) promise that my first use would be free. Faced with a £50 fee to try to solve what to me seemed to be a Hub 5 issue, I decided on a different approach - I bought a small USB Wi-Fi adaptor (TP Link 802.11ac) (which was still cheaper than spending £50! on VM support). The plug in adaptor seemed to do the job, but occasionally had its own issues - interruptions in connectivity.
In the end, I set up a Wireless MAC filter using the MAC address of the SP4. I then used this filter to deny the SP4 access to the Hub's 5 GHz network. I didn't need restrict any other device. Once applied, my SP4 was happy once again and enjoys great Internet access (albeit restricted to the 2.4 GHz band).
Since I didn't make any change to the SP4 itself. I can still benefit from the 5 GHz AC performance if I connect to another (non VM Hub 5 router). Until the Hub 5 gets fixed, setting up a MAC filter on the Hub seems the best compromise.