Subdomain is not resolving if it is configured as a Forward zone AND this DNS server is authoritative for the Domain

IF the OES DNS server is authoritative for a domain
AND it is also authoritative for a subdomain that was created as a Forward zone
THEN name resolve for anything in the subdomain results in an NXDOMAIN error.

The OES DNS server does not attempt a forward for any queries in that subdomain.

If the subdomain is instead for a different domain that this DNS server is not authoritative for then forwarding occurs as expected.

Example Config:

DNS1
mycomp.zone - Primary
lab.mycomp.zone - Forward to DNS2
test.other.zone - Forward to DNS2

DNS2
lab.mycomp.zone - Primary
test.other.zone - Primary

Test
Pointing at DNS1 all records resolve in mycomp.zone
Pointing at DNS1 no records resolve in lab.mycomp.zone
 - Looking at a LAN trace there are no attempts to forward to DNS2 at all.
   - tcpdump -any -s0 host dns2 and port 53
Pointing at DNS1 all records resolve in lab.other.zone because this one does forward as can be seen in the same LAN trace output.

Create the subdomain as a Secondary zone rather than a Forward zone.