In my experience, whilst they believe what they're saying, a lot of it not always accurate.
(When I asked my engineer if it was OK now to switch it from router to modem mode he said it was already in modem mode. I showed him that it was in router mode with the Wi-Fi turned off and he said that was modem mode! I showed him that there was a separate menu option for modem mode which meant my own router would get an external IP address - he just looked blank and said he didn't know anything about computers.)
Yes you can turn off the Wi-Fi on the SH3. Running the SH3 in router mode should at least stabilise the behaviour of the Asus. But I strongly suggest that once you have that sorted out you have a look at the network log of the SH3. If it's a provisioning issue it can only fixed by the VM support people, not the engineers or a firmware update.
Unfortunately the only thing you can do is reboot the hub occasionally to see if it has been pushed out in your area. But it should do it by itself within 24 hours of becoming available.