We are investigating this issue internally. We have reproduced it. Our intial investigations show that the Digital Unix client sends a readdir request and we respond to it. We mark in our reply that we are not at the end of the directory, but the client never comes back for more. Our suspicions are that the client is deciding it has all of the directory information based on some client side cached information or the cookie we pass back. We have not yet determined with certainty whether it is a client or server bug.
For what it's worth, we had a similar bug with Sun clients and NFSv2 at one point.
The problem then was that we were sending back a packet with the "I have more directory data flag" set, but we didn't actually include any directory entries in the packet. Despite the "I have more directory data flag" being set, the client didn't ask for any data.
The chances seem low that this same issue re-emerged in NFSv3, but I thought the info might be useful anyway.
Dave