We have found that there are more than one WBS for an object. This is
supposed to be a unique relationship i.e. one to one.
On doing an object find for a Project Characteristic you obtain the
object numbers (that is WBS elements internal numbers) of the objects
that contain the characteristics. Using T.code SE16 you can find the WBS
element number of the object. On doing this search we have found
multiple WBS elements for the same object number. On investigating the
situation, we found that in most instances the "other" object another
WBS element in the same structure or one created shortly after the
correct WBS element.
We have not yet found out why this happens, what the solution is or if
we have found all occurrences.
In PRPS, there is 4 fields that refer to an SAP object:
POSID is the WBS element identifyer the user see on the screen
PSPNR is the internal SAP project item number (which IS unique)
OBJNR is the SAP object number (made out prefix 'PR' and the internal
project item number. It is also the number that is stored in the Costs tables.
PSPHI is the internal current number of the project the WBS element belongs
to.
All these numbers are absolutely unique. But all WBS elements in the same
project will share the same PSPHI, which indicates the project (from the
PROJ database).
The reason why you have an internal SAP number (PSPNR) and an external
number (POSID) is to allow the user to change the WBS element identifyer
without losing all the history.
Check to make sure you were looking at the right object number.