I only have the smart modem without the mesh, and did have the DHCP lease problem. I have not noticed DHCP problems since I turned off band steering - probably two weeks ago. This does not mean that much on its own as it is as likely to be coincidence as anything.
I turned off band steering yesterday and will see in a couple of weeks whether that makes any difference. For me wired clients have never had DHCP issues so fingers crossed this will help. As an FYI as soon as a turned band steering off my Mac book renewed its lease no problem which it hasn’t been able to for a couple of days despite a router restart.
Okay, so it’s been just over two weeks since I turned off band steering and my wifi has been working flawlessly. No drop outs, no dhcp issues and no intermittent issues trying to connect clients. It’s only 2 weeks but it’s the best run I’ve had with this kit all year and seems consistent to what @nzmatt mentioned.
I’ll let people know if issues crop up again but feels like bandsteering is part of the problem.