Issue with At Completion Cost from assignment spread

When creating a report in BI Publisher containing values from the assignment spread I have an issue with the At Completion Cost field.

In my report At Completion Cost only equal Actual Cost + Remaining Cost when the assignment have a role or a resource. When the assignment have both a role and a resource At Completion Cost is empty. There is no issue with At Completion Units.

Any idea what could be causing this?

Version: P6 17.12.4.0

Query:

select

     sum(RAS.ACTUALUNITS),

     sum(RAS.ACTUALCOST),

     sum(RAS.REMAININGUNITS),

     sum(RAS.REMAININGCOST),

     sum(RAS.ATCOMPLETIONUNITS),

     sum(RAS.ATCOMPLETIONCOST)

from PXRPTUSER.RESOURCEASSIGNMENTSPREAD RAS