the hub resetting about every 14days is a common thing but it normally reconnects immediately at the same speed and noise margin after as it had before it can be annoying but nothing you can do apart from get a third party router
have you turned of smart setup?
Have you split the 2.4/5ghz networks and also selected channels manually rather than automatic
many on the forum opt for the tplink 9970 at about £30 and are happy with the result
My smarthub reconnects every 16 days now. It used to be every 14 days, then back in July last year it received a firmware update and had continuous connection for weeks. In the last couple of month every 16 days it reconnects. Always with the same sync speed (72.10Mbps) though and always at the same time at midnight. As long as it keeps this speed I'm quite happy and not bothered with this 16 days cycle...