PPP - all dialout ports busy

[slvz]

I still have a HPUX B.11.31 system.  It conducts dialout ppp connections that began failing with 'Can't open 'culxxxx' ; Device Busy error.    No changes occurred on the system.  I can alter ppp config to deploy other cul devices on the system and get the 'busy' error for all .   I have confirmed the devices are not tied up, have rebooted, have even rebuilt device files among other actions.    The modems look fine which I can prove by dialing out using other software.   Can anyone advise?