DNS stops working for wifi clients after a while... (local destination)

pastic

Epilogue :
I found the culprit. I had to enter a host override in the wireless AP as well (openwrt). The AP is running a DNS forwarder, but even though I point it to my pfsense DNS server, it would not work without the host override.

Hi,
I have had a Nextcloud server running at home for several years and suddenly, most of the time, I cannot reach it any longer from wireless devices in my home. I do not understand where the point of failure is.

LAN interface is for wired devices 10.0.0.0/24
OPT1 is for wireless 10.0.1.0/24
Nextcloud server lives on LAN at 10.0.0.200 and has a self-signed certificate and can be reached at https://nextcloud.nibelheim from within my home network due to a host override in pfsense.

Devices on LAN never have access problems when using https://nextcloud.nibelheim, wireless devices on OPT1 have begin to have problems but can sometimes access (after numerous server restarts, firewall reboots and clearings of cache on the wireless device). But after successful contact for a few hours they invariably "disconnect" and then the situation below unfolds.

My Android 14 phone is my test case:

Native Chrome browser can always resolve nextcloud.nibelheim and always reaches the server GUI.
Firefox and Firefox Focus will sometimes resolve but most of the time not ("Address not found")
The Nextcloud Android app will sometimes connect but most of the time says "Server not reachable"
If I reinstall Nextcloud Android app and try to reconnect my account the app complains "Could not find host 'nextcloud.nibelheim' "
If I try to connect using https://10.0.0.200 I get SSL errors no matter what device I try on (guess that's because of the self-signed certificate?)
DavX5 app that manages calendar and contacts sync between the phone and the Nextcloud server stops syncing and complains "Network or I/O error: Unable to resolve host 'nextcloud.nibelheim'. No address associated with hostname."

But from the same phone I can run a DNS lookup and it seems 'nextcloud.nibelheim' resolves fine for both IPv4 and IPv6 !!

I am aware there a lots of variables here, but maybe someone can spot what is going on? I'd be super grateful for pointers. I insert below some images of configs and DNS lookups.

root@nextcloud:~ # ifconfig
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> metric 0 mtu 16384
	options=680003<RXCSUM,TXCSUM,LINKSTATE,RXCSUM_IPV6,TXCSUM_IPV6>
	inet6 ::1 prefixlen 128
	inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1
	inet 127.0.0.1 netmask 0xff000000
	groups: lo
	nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
pflog0: flags=0<> metric 0 mtu 33160
	groups: pflog
epair0b: flags=8863<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
	options=8<VLAN_MTU>
	ether ae:1f:6b:ba:b5:82
	hwaddr 02:c3:53:97:36:0b
	inet 10.0.0.200 netmask 0xffffff00 broadcast 10.0.0.255
	inet6 fe80::ac1f:6bff:feba:b582%epair0b prefixlen 64 scopeid 0x3
	groups: epair
	media: Ethernet 10Gbase-T (10Gbase-T <full-duplex>)
	status: active
	nd6 options=23<PERFORMNUD,ACCEPT_RTADV,AUTO_LINKLOCAL>