Q:
I'm having problems assigning or unassigning a PL-11 in System Manager
A:
From firmware version 1.71 it is possible to assign PL-11 from the communications options menu.
Once assigned, if an older version configuration is loaded, the older configuration will not recognise PL11 and therefore you will not be able to un-assign it.
PL11 can only be assigned and unassigned in firmware version 1.71 and higher.