COM Port not free on a PortServerTS

After some cycles of use (open com / use / close com) the port remains in open state. Only help is to reboot the PortServer over the WEB Interface.
Version is: 82000747_W 10/23/2013
Driver: 4.7.410
Ser Nr: E51871064

Is this a known issue ?
Another device works correct.

This is not a known issue.

If you telnet/SSH to the unit, login as root and issue the “who” command, does it show that the port is in use?

If so, you should see which host has the port open and pursue closing it.

If you are not able to close it from the host computer, you can issue the kill command from the prompt:

#> kill tty=(port_number)

Telnet works, but it does not show any port in use and also no host which opens the port. Kill command works successful, after that the port is available again. It seems to be only port4 of the device.

We are experiencing the same issues with not only the same version, but others as well (82000903_J3 09/05/2003). This happens when rebooting the system as well.