lines going "down"

Hi all.  We were using conserver 7.0.0 for several months, but ports
seemed to get stuck too often, forcing me to restart the daemon, so I
upgraded to 7.1.3.  Unfortunately, things have been worse under this
version.  More often than not, ports suddenly go "down", and restarting
the server makes some ports come up and others go down.

Is there some better in-bewteen version I should try?  I'm starting to
get frustrated.  

 oracle1                    down <none>
 pbxp1                      down <none>
 sunray1                    up   <none>
 sunray2                    up   <none>
 cisco                      up   <none>
 jtsd07                     up   <none>
 jtsd08                     up   <none>
 jtsd09                     up   <none>
 toro                       up   <none>
 shasta                     down <none>
 tahoe                      down <none>
 vodavi                     up   <none>

Right now, the four shown "down" should be "up".  Five minutes ago,
jtsd0[789] showed "down" for no explicable reason.  'netstat' shows no
active connection between the conserver and the terminal server for the
"down" ports.  ^Eco just comes back with "line is still down".

We are using a Portmaster PM2e.  Any help or suggestions would be
appreciated.  Thank you.