If you think that you have a BB speed problem, then to check the speeds coming in to your Hub properly, and whether they match what you should be getting, you cannot rely on wifi tests, - no BB supplier guarantees those - only speeds "TO" the Hub are guaranteed.
So, can you test speeds directly like this. As you expect >100Mbps then connect a 1GB enabled computer/laptop, with up to date drivers, via a known good and working Cat5e (or better) ethernet cable, directly to the Hub which you have put into “modem mode”. Test at speedtest.net (not the App!) to your nearest VM server - try on 2 different browsers.
If they are still low – boot the device into safe+networking mode and try again.
There are many posts on here where unknown software, corrupted browsers or other connected devices are limiting speeds on tests.
Report back what that gets.
-------------------- John --------------------
My services: HD TV on VIP (+ Sky Sports & Movies & BT sport), x3 V6 boxes (1 wired 2 WiFi,) SH2 in modem mode with Airport Extreme Router. On VIVID200, Talk Anytime Phone, x2 Mobile SIM only iPhones.