Not sure - but I think that that router is only Wifi5? If so it will never deliver full speeds over wifi.
Not sure why its dropped - I would suspect some QoS in operation somewhere
Test it on ethernet cable connection and see what that gets
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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.