dnsmasq.postconf Adds Interface to Desired DNS Address

[GHammer]

I've run this config for a while (>6 months) with no problems. Redirect all devices to my pihole for DNS.
Today, after applying 384.18 beta 1 to both the AX58U and the 86U AP I'm seeing the interface being added to the IPv6 DNS address.

Wired is fine.

P6.DNS[1]:                             fe80::da16:4c05:d30d:efd6

Wireless though gives:

fe80::da16:4c05:d30d:efd6%wlan0

Here's the script used:

#!/bin/sh
sed -i "s/dhcp-option=lan,option6:23,.*/dhcp-option=lan,option6:23,[fe80::da16:4c05:d30d:efd6]/" $1
echo "dhcp-option=lan,6,10.10.100.2" >> $1

The script is being run on the 58U of course.

Ideas are welcome