But I’m also seeing issues with other sites like enterprise.com and southwest.com that don’t appear to use Akamai DNS.

I think they do: $ dig www.enterprise.com ; <<>> DiG 9.11.3-1ubuntu1.15-Ubuntu <<>> www.enterprise.com ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 56312 ;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 8, ADDITIONAL: 10 ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ;; QUESTION SECTION: ;www.enterprise.com. IN A ;; ANSWER SECTION: www.enterprise.com. 571 IN CNAME ehi-prod-ecom.edgekey.net. ehi-prod-ecom.edgekey.NET. 21571 IN CNAME e38647.dscx.akamaiedge.net. e38647.dscx.akamaiedge.net. 20 IN A 23.198.7.180 e38647.dscx.akamaiedge.net. 20 IN A 23.198.7.176 ;; AUTHORITY SECTION: dscx.akamaiedge.NET. 1727 IN NS n6dscx.akamaiedge.net. dscx.akamaiedge.NET. 1727 IN NS n1dscx.akamaiedge.net. dscx.akamaiedge.NET. 1727 IN NS n4dscx.akamaiedge.net. dscx.akamaiedge.NET. 1727 IN NS n2dscx.akamaiedge.net. dscx.akamaiedge.NET. 1727 IN NS n3dscx.akamaiedge.net. dscx.akamaiedge.NET. 1727 IN NS n0dscx.akamaiedge.net. dscx.akamaiedge.NET. 1727 IN NS n5dscx.akamaiedge.net. dscx.akamaiedge.NET. 1727 IN NS n7dscx.akamaiedge.net. $ dig www.southwest.com ; <<>> DiG 9.11.3-1ubuntu1.15-Ubuntu <<>> www.southwest.com ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 64049 ;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 8, ADDITIONAL: 11 ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ;; QUESTION SECTION: ;www.southwest.com. IN A ;; ANSWER SECTION: www.southwest.com. 300 IN CNAME www.southwest.com.edgekey.net. www.southwest.com.edgekey.net. 300 IN CNAME e7466.a.akamaiedge.net. e7466.a.akamaiedge.net. 20 IN A 23.35.160.178 ;; AUTHORITY SECTION: a.akamaiedge.NET. 1673 IN NS n1a.akamaiedge.NET. a.akamaiedge.NET. 1673 IN NS n0a.akamaiedge.NET. a.akamaiedge.NET. 1673 IN NS n4a.akamaiedge.NET. a.akamaiedge.NET. 1673 IN NS n2a.akamaiedge.NET. a.akamaiedge.NET. 1673 IN NS n7a.akamaiedge.NET. a.akamaiedge.NET. 1673 IN NS n6a.akamaiedge.NET. a.akamaiedge.NET. 1673 IN NS n5a.akamaiedge.NET. a.akamaiedge.NET. 1673 IN NS n3a.akamaiedge.NET.