unable to resolve *.irs.gov at local bind 9.12.0 server ?

[PGNet Dev]

I've a local bind 9.12.0 server.  Works for virtually all domains.

For "irs.gov", it fails,

	dig A irs.gov

		; <<>> DiG 9.12.0 <<>> A irs.gov
		;; global options: +cmd
		;; Got answer:
		;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 2101
		;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

		;; OPT PSEUDOSECTION:
		; EDNS: version: 0, flags:; udp: 4096
		; COOKIE: 924396a00e82e7e6cb3a18495a6cb893e564a4fc00f78373 (good)
		;; QUESTION SECTION:
		;irs.gov.                       IN      A

		;; Query time: 2706 msec
		;; SERVER: 127.0.0.1#53(127.0.0.1)
		;; WHEN: Sat Jan 27 09:36:19 PST 2018
		;; MSG SIZE  rcvd: 64

Resolution is fine at offsite servers

	dig A irs.gov @8.8.8.8

		; <<>> DiG 9.12.0 <<>> A irs.gov @8.8.8.8
		;; global options: +cmd
		;; Got answer:
		;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 56261
		;; flags: qr rd ra ad; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

		;; OPT PSEUDOSECTION:
		; EDNS: version: 0, flags:; udp: 512
		;; QUESTION SECTION:
		;irs.gov.                       IN      A

		;; ANSWER SECTION:
		irs.gov.                236     IN      A       166.123.218.220

		;; Query time: 43 msec
		;; SERVER: 8.8.8.8#53(8.8.8.8)
		;; WHEN: Sat Jan 27 09:36:29 PST 2018
		;; MSG SIZE  rcvd: 52

looking at local server trace,

	dig +trace irs.gov

		; <<>> DiG 9.12.0 <<>> +trace irs.gov
		;; global options: +cmd
		.                       3328    IN      NS      a.root-servers.net.
		.                       3328    IN      NS      b.root-servers.net.
		.                       3328    IN      NS      c.root-servers.net.
		.                       3328    IN      NS      d.root-servers.net.
		.                       3328    IN      NS      e.root-servers.net.
		.                       3328    IN      NS      f.root-servers.net.
		.                       3328    IN      NS      g.root-servers.net.
		.                       3328    IN      NS      h.root-servers.net.
		.                       3328    IN      NS      i.root-servers.net.
		.                       3328    IN      NS      j.root-servers.net.
		.                       3328    IN      NS      k.root-servers.net.
		.                       3328    IN      NS      l.root-servers.net.
		.                       3328    IN      NS      m.root-servers.net.
		.                       3328    IN      RRSIG   NS 8 0 518400 20180209050000 20180127040000 41824 . DkeMZSxEcmxZ78udDb9pw7HxLylmNUJb4utqwV206pQ+ItBvuuJzMnmY pboHDZPEn15xUcGTmnAmDfpX1fhoHPYuBiXC3DmO/gwRG1ktl/xRKbjE m9E9PDvUmd1F+/FCcexTFsFm0RU/EMiziKIYJL1ttj2+Ozjc/j+ii6I9 cOVwjH8DE+3XqGjti803qu4Ycr3MQYcPxQiO6NckxoidZM3GxZRkunmr mOz5bBDFfOBMbgC4uYGpfVuJ1OysDRzniNuFQXkftIlpFHmgeIi3U/GR RoeIuOip9YaJRiUfnK1V8iFaff/70YvPr6PQkpmb8NpayLdfDqQdsK3D 8rJORA==
		;; Received 565 bytes from 127.0.0.1#53(127.0.0.1) in 1 ms

		gov.                    172800  IN      NS      a.gov-servers.net.
		gov.                    172800  IN      NS      b.gov-servers.net.
		gov.                    172800  IN      NS      c.gov-servers.net.
		gov.                    172800  IN      NS      d.gov-servers.net.
		gov.                    86400   IN      DS      7698 8 1 6F109B46A80CEA9613DC86D5A3E065520505AAFE
		gov.                    86400   IN      DS      7698 8 2 6BC949E638442EAD0BDAF0935763C8D003760384FF15EBBD5CE86BB5 559561F0
		gov.                    86400   IN      RRSIG   DS 8 1 86400 20180209050000 20180127040000 41824 . jqlemnm+YBXTy0W+akzROVZNlZBsvyVnDOyCONEyDiOn4fXWTrFiDdXD lvq60ytuyQpaevkMQHC360Z5CIU4GRqODFom0G/v1whZOS140lBiqPVb f9xpX29Fx/RjEekGNXMlzXyrzXCtvy2yFQ7jcUYwl/JJ5DFRZerjAAt8 7v/CdHrF42E5ocjcSnxMZ1EaUFBMAm549lYRVSOG4h6SSlfos4R/G8GF VKXs2JE27/EWXdIw0uMZKU88ExLdY6TVpCNHrrJ29W6CIT5JO59sI8GO woML2fwF7+gfM5zbNM5geHdOvAVh0KY1mhCRT8cln5r8maazH4ih+jvV akgTRQ==
		;; Received 662 bytes from 199.7.83.42#53(l.root-servers.net) in 28 ms

		irs.gov.                86400   IN      NS      ns1.irs.gov.
		irs.gov.                86400   IN      NS      ns2.irs.gov.
		irs.gov.                86400   IN      NS      ns3.irs.gov.
		irs.gov.                86400   IN      NS      ns4.irs.gov.
		irs.gov.                3600    IN      DS      29552 8 2 A9B81C7EDC4E5DBEF97991A812FCE87E82E80BF2330C3FB75C36DBFE 665745A3
		irs.gov.                3600    IN      RRSIG   DS 8 2 3600 20180203161006 20180127161006 21179 gov. LNdq0+IpiPLViVoHC/UU4mCtQquIGY/BRMxWWsZ07UbTa6q7ZkVRIvwM RRLZz4lUb8pOddpuRqoqcVtbCL9hTfUHexxOsRUGdZOxDpfR5iIgKqcQ dTd/R6oyUqM9vbHu5u5S9MSlzN0ZWHcqxiIlpG7UL2TenZcugLkjEwT+ hdE=
		couldn't get address for 'ns1.irs.gov': not found
		couldn't get address for 'ns2.irs.gov': not found
		couldn't get address for 'ns3.irs.gov': not found
		couldn't get address for 'ns4.irs.gov': not found
		dig: couldn't get address for 'ns1.irs.gov': no more

checking

	ns1.irs.gov
	ns2.irs.gov
	ns3.irs.gov
	ns4.irs.gov

the issue's the same -- no resolution at the local server, just fine offsite.

What's going on here, specific to *irs.gov?

Is it 'them'? Is there something we can remediate at the local server?