When I change the Planned Start or Complete dates on an event the Planned Duration does not recalculate
This is working as designed. When an event is first created the Planned Duration is calculated from the dates entered as a guideline. But thereafter it can be manually overridden and will not be automatically updated so as not to overwrite any manual changes. For example an Abnormal Load event could have Planned Start/Complete dates months apart (as they don’t know precisely when it will occur), but the Planned Duration of the event itself may only be a few minutes or hours (i.e. the duration the Abnormal Load takes to travel along the network).