How long you are seeing this behaviour? Doesn't the cache disappear after a while? It is supposed to, based on the options nfs.export.****.timeout (assuming this is 7 mode)
Sorry to ask this, but just to make sure that we are not missing any pieces, Did you run the exportfs command from the Client or the Data ONTAP CLI?
If the NFS export is from a vfiler, you should run this exportfs command through "vfiler run".