dyndb system test failing intermittently.

S:dyndb:Tue Dec  4 02:47:36 UTC 2018
T:dyndb:1:A
A:dyndb:System test dyndb
I:dyndb:PORTRANGE:8000 - 8099
I:dyndb:adding test1.ipv4.example.nil. A 10.53.0.10 (1)
I:dyndb:adding test2.ipv4.example.nil. A 10.53.0.11 (2)
I:dyndb:adding test3.ipv4.example.nil. A 10.53.0.12 (3)
I:dyndb:adding test4.ipv6.example.nil. AAAA 2001:db8::1 (4)
I:dyndb:deleting test1.ipv4.example.nil. A (was 10.53.0.10) (5)
I:dyndb:deleting test2.ipv4.example.nil. A (was 10.53.0.11) (6)
I:dyndb:deleting test3.ipv4.example.nil. A (was 10.53.0.12) (7)
I:dyndb:deleting test4.ipv6.example.nil. AAAA (was 2001:db8::1) (8)
I:dyndb:checking parameter logging (9)
I:dyndb:checking dyndb still works after reload
I:dyndb:ns1 server reload successful
I:dyndb:adding test5.ipv4.example.nil. A 10.53.0.10 (10)
I:dyndb:dig reverse output incorrect for test5.ipv4.example.nil. A :
I:dyndb:adding test6.ipv6.example.nil. AAAA 2001:db8::1 (11)
I:dyndb:deleting test5.ipv4.example.nil. A (was 10.53.0.10) (12)
I:dyndb:deleting test6.ipv6.example.nil. AAAA (was 2001:db8::1) (13)
I:dyndb:exit status: 1
R:dyndb:FAIL
E:dyndb:Tue Dec  4 02:47:38 UTC 2018

Nothing obvious in named.run. The PTR lookup returned NXDOMAIN.