Core Issue
After the upgrade, when a Calling Search Space (CSS) is assigned at both the Distinguished Name (DN) level and at the device level, then the phone cannot find the Call Park number in those partitions specfied by the CSS.
In such situations, if any cCall Park numbers are available in null partition (not assigned to any partition), they are improperly selected and used.
Resolution
This problem is documented in Cisco bug ID CSCef49861.
This defect exists in Cisco CallManager 4.0(2a) and Cisco CallManager 4.0(2a)ES01. It is fixed in Cisco CallManager 4.0(02a)ES03.
To obtain an appropriate Engineering Special (ES), open a service request in the Cisco Technical Assistance Center (TAC) Service Request Tool.
For a workaround, do not set both DN CSS and station CSS.
For more information on Call Park, refer to Call Park.