18.06.5 neighbor discovery protocol failure on bridge

I'm running 18.06.5 on an internal router that I've configured as a pure bridge for lan to WIFI bridging. Essentially DHCP, firewall and odhcpd have been turned off in the luci startup menu and the ethernet has been plugged into the lan port. (I've also removed the wan and wan6 interfaces and configured the switch to put the wan ethernet connector on the lan, but that shouldn't effect the bug.)

When I have my laptop plugged into the ethernet I see a default ipv6 route pointing to the main router. I see the router's MAC address in the the neigbor table. When I unplug the ethernet the default route correctly goes away but even though the WIFI bridge is working correctly for ipv4 and I can connect to the internet, I can't do the same for ipv6. There is no default route, just one route for the loopback and another for the the wifi network's local network. I also see a single neighbor table entry for what I assume is the AP's wifi interface but it is marked as STALE.

I had previously tried to set up the AP as a true non-NAT router, but failed. Too many things didn't work very well. I may well have been seeing this bug for a while but never characterized it.

hardware: Netgear 3700v4

This is from the wifi-connected laptop:

root@tosca ~]# ip -6 neigh
fe80::f29f:c2ff:fe16:8039 dev wlp3s0 lladdr f0:9f:c2:16:80:39 router STALE
[root@tosca ~]# ip -6 route
::1 dev lo proto kernel metric 256 pref medium
fe80::/64 dev wlp3s0 proto kernel metric 600 pref medium
[root@tosca ~]# ip neigh dev wlp3s0 lladdr f0:9f:c2:16:80:39 REACHABLE dev wlp3s0 lladdr 08:60:6e:74:6f:e2 REACHABLE dev wlp3s0 lladdr b8:3e:59:aa:cd:f6 STALE
fe80::f29f:c2ff:fe16:8039 dev wlp3s0 lladdr f0:9f:c2:16:80:39 router STALE
[root@tosca ~]# ip route
default via dev wlp3s0 proto dhcp metric 600 dev wlp3s0 proto kernel scope link src metric 600 
[root@tosca ~]#