Custom DNS ignored after reboot

I've got an Eero Pro 6 and two 6+'s on my home network, using a Raspberry Pi with pi-hole for DNS. All of these are up to date on patches/releases.

I reboot my wifi network overnight (EMF's) so it's off from midnight to 6am. The raspberry pi currently stays on. When the Eero's come back online, my network works, but it ignores my custom DNS config. No reboots of any network items fix the DNS, the only thing that seems to solve the problem is to set the Eero's to default DNS and then back to the same custom DNS.

I'm not using any Eero plus features, HomeKit, DNS caching, etc

any ideas appreciated!