Anyone else got issues with frequent WAN drop outs on Fibre along with observed short DHCP leases from OneNZ (Christchurch)? I'm talking leases of 230 to 600 seconds. I'd expect a DHCP lease on fibre to be 4 hours up till a day.

I'm still using an old Vodafone UltraHub router that connects to a Huawei EchoLife HG8240H ONT.
The UltraHub is a bit of a POS but I can't fault it in this instance. It's event logs show 
`Removing intercept reason: "wan_down"`
shortly before a lease renewal like
`Switching to bound; server 10.0.0.100 assigned ip [Public IP] (leasetime 599 T1 299 T2 524)`

thinking it could be my dodgey Ultrahub. I connected to the ONT directly with a linux PC and brough up the ethernet on the WAN port spoofing the ultrahub MAC address.
I set up a vlan dhcp client and got it to make DHCP requests successfully. And I saw the same short leases being issued.

I've "chatted" to at least 2 of the their supports (I really hate their chat support service, it takes forever). They say they log onto the ONT and can't see anything wrong. Eventually one tech guy copy and pasted a DHCP service definition to me and suggested why the leases would be shorter in times of high demand to remove stale clients. When I pointed out that fibre connections are normally pretty constant and don't churn much compare to WiFi, he then just says, that the short leases are normal for their service. He then proceeded to suggest I buy one of their Deco Modems. I can't see replacing the router/modem would be of any benefit when
1. I see the same behavior on multiple devices
2. The leases are issued by them
3. They couldn't actually pinpoint anything wrong with my router.
4. The router's WAN connection is stable 99% of the time ... except when the leases are expiring.

The Deco Modem's apparent draw card is the mesh wifi ... which does nothing to address WAN stability.

I'm assuming if they are dynamically shortening their leases to 240 seconds etc... then their network must be over saturated. What do you think?
It's like this at any time of day.

Any suggestions from anyone?