That's a top notch Asus router and you should have no issues with it. Can you try setting it up again from scratch as per below - using a new Cat6 ethernet cable and see if the issues persist
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Then, set up your Asus with port set to be in DHCP & Nat mode, it may be pre-set that way anyway.
Then disconnect all cables from your Asus and unplug it.
Put the VM Hub into modem mode (
https://www.virginmedia.com/help/virgin-media-hub-modem-mode ) and wait for the base light to turn magenta/purple (on a Hub3 - but not on a Hub4!). Once it’s in modem mode, the VM hub “MUST” then be powered off.
Then put in the WAN cable from the Asus into the VM hub. NOW… power up the VM hub and leave it ~5' to initialise and you should get a connection. This order only needs to be done the first time you connect the router to the VM hub
See if that stabilises things
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John
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I do not work for VM. 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 +2 Airport Express's. On VIVID200, Talk Anytime Phone, x2 Mobile SIM only iPhones.