Either a host is not accessible, resulting in timeouts or an entry is in one of the pre-aliases files twice.
The second one of these results from GCOS field combinations making the same mail alias. Look at the pre-aliases file corresponding to the host and look for multiple definitions of the reported alias. Then refer to the host's NIS server's password file and see what you can do to prevent multiple aliases, e.g. you might be able to tag an extra letter to the end of the GCOS field to make the two entries different.
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