Always with tunish on the screen ? Nover a message ?
ucx sho servi telnet/fu doesn't show "peak" as high as "limit" ?
Did you try disable servi telnet , wait a few seconds, ucx enable servi telnet ? That should normally help (but kill all users).
Did you check quotas tcpip$inetacp ? Opcom messages ? Accouting of the process (may be it aborted the telnet after leaving the screen blocked/client unabortable) ?
Wim
Wim