The client could release an object handle while at the same the
handle was on the wire from the server to the client.
The client then expected a serialized object which the server didn't
send because the handle not yet release by the client at the time it
was sent.
Solution:
The client and server both count how many times an handle is send from
the server to the client. The client object release only succeeds if the
counters match, to be sure no handles are "on the wire".
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