It would be important to know whether the RealPort driver is in use on the HP/UX server and what version.
Also, the firmware version and port configuration on the PortServer II would be helpful. From the PortServer II root prompt:
#> set config
The firmware version displays at the top of the screen, be sure the most current version 3.1.12 is installed. If not, the current firmware and driver is available from our web-site at:
To check the port configuration from the PortServer II root prompt:
#> set ports ra=*