1 of 2 Pi-Hole's stops working after X hours...

Hello guys, one of my Pi-Hole’s keeps breaking after just a few hours running and I can’t figure out why?!

Expected Behaviour:

Testing an internal Domain name nas.domain.com should give the following results…

Header:
ID=1, QR=Response, Opcode=QUERY, RCODE=NO ERROR
AuthoritativeAnswer=Yes, Truncation=No
Recursion Desired=Yes, Recursion Available=Yes
QDCOUNT=1, ANCOUNT=1, NSCOUNT=0, ARCOUNT=0

Question:
Name=nas.domain.com, QTYPE=A, QCLASS=INET

Answer Section:

I find I get the above results on my Pi-Hole at home running on Rasbian I get this 100% of the time as expected as this entry is in it’s LAN.LIST file.

Actual Behaviour:

My VPS Server running Ubuntu 18.04 and Pi-Hole also get this result initially and also has the entry in it’s LAN.LIST file.

However aftrer just a few hours name resolution starts getting odd…

Header:
ID=1, QR=Response, Opcode=QUERY, RCODE=NAME ERROR
AuthoritativeAnswer=No, Truncation=No
Recursion Desired=Yes, Recursion Available=Yes
QDCOUNT=1, ANCOUNT=0, NSCOUNT=1, ARCOUNT=0

Question:
Name=nas.domain.com, QTYPE=A, QCLASS=INET

Authority Records Section:

But this only seems to apply to some LAN.LIST entries, it just seems to stop reading that file as there is another subdomin I have, this time however there is a public DNS entry in existence too where as the previous was purely a local entry, well after it’s in this state suddenly instead of reporting the LAN IP to me, it reportrs the WAN IP ignoring the entry set in LAN.LST?!

What’s going on?

Interestingly I find that restarting the DNS Server to resolve this is not enough, I need to restart the whole system, maybe I can get away with restartibng PiHole serivce not tried need to check.

Debug Token:

https://tricorder.pi-hole.net/vj1nhbl7hq