Also you havent said whether this is happening on devices connecting on ethernet cables at the same times as the wifi ones drop off - if you dont know can you check/test that?
First do a quick check that all of your coax cable connections are in nice and "finger" tight - at the Hub and wall box and also at any splitters/attenuators/etc. Ensure there are no “unterminated cable loose ends. Disconnect all the connections and reconnect to be sure. Also check that the internal wiring is ok with no kinking or chaffing, check that all looks good with the outside cabling and wall box.
Then, you could first try a factory reset – a lot of the VM techies on here suggest it as a first option and it has worked for many customers.
Note that a pinhole reset on a Hub3 can be a bit problematic - so do it EXACTLY this way (not as the VM website says!).
Firstly, make sure the Hub's sticker/card with the two passwords on it is still there and legible or you will be stuffed ! If its not – DON’T DO IT !
With the Hub switched "on", disconnect any ethernet connections and then push in the “reset pin” with the end of a paperclip/thin nail/SIM tray “tool” or similar (bigger items like ball point pen ends may not press it in far enough) until you feel it at the “stop point” and hold it there firmly for a "timed" minimum of 60 seconds do NOT restart the Hub after that. Leave it 10' or so to stabilise and then your passwords/passphrase for both the Hub settings and the Wifi networks will revert to the two printed on the Hub sticker on its base/side/card. Make sure you use the wifi one for devices connecting to the wifi and the settings/admin one to access the Hub (it is a six digit numeric one).
See if that stabilises it - if not come back here and there are other diagnostics we can do such as you posting up the Hub stats/data and starting a Broadband Quality Monitor - that will help diagnose what the issue is and whether it needs a Tech visit or not.
-------------------- 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.