This looks like a failure to support an essential component of the Samba feature set. If the failing feature is part of the RFC for Samba, this isn't about Red Hat client, but about adherence to standards.
In my case just now, the workaround to turn spneg off seems to work. Not exactly a nice way to have to deal with this. What changed in the standards that the NetApp support for Samba isn't keeping up with?