Resolved.
I copied the LIST, MEMBERSHIP, TELNET archives and related index files of the copy of the directory of the day before in the official directory in use and everything is back as before.
I don't understand what happened but the important thing that I solved the problem.
I would be grateful if anyone could hypothesize the reason that could have caused this anomaly.
Thanks.
73's de IKØCHU Mauro
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IKØCHU Mauro