Outbound Policy + VLAN bug in 8.5 and 8.4.1

Same thing has happened again, running 8.5.2 5739.

After working normally for about 10 days, I noticed my hot tub had gone offline again. I could connect to it over the VLAN, but it could not connect from the VLAN over WAN to the cloud server. Reason: DNS was failing.

Here are my DNS settings:
Network
image

VLAN-Specific:


This setting works, but fails after about 10 days:

To work around the bug, I need to hard-code the DNS server IPs:

I don’t know what’s exactly going wrong, but it’s repeatable.

My theories:

  • DNS server for the VLAN is crashing (but perhaps only for VLAN Ethernet devices?)
  • Firewall starts blocking DNS requests (but only for Ethernet VLAN devices?)
  • Gremlins?