If the clustername is the same as the zone name, Windows will default to using NetBIOS resolution and connects to the first node only.    “They are using the fully qualified “A” record name as the SmartConnect Zone Name.”  This is incorrect. The A record would be a single IP address. That means that Zone name will resolve to a single IP instead of a delegated DNS entry.  Are they using BIND or a Windows DNS server?
OK, we opened a case with Isilon Support.   We went though that and now everything is resolving to a single node, including the ones that were working properly.   Everything looks right to me on the DNS side.   Does the Smart Connect Zone Name need to be something completely different?   They are using the fully qualified “A” record name as the SmartConnect Zone Name.
SmartConnect only resolves to one node