This issue has been observed in CA PPM 15.1 and 15.2.
This issue is caused by DE32783.
Engineering has fixed this issue in Clarity PPM 15.3 and has backported the fix to Clarity PPM 15.1 patch 7 and 15.2 patch 3.
Note: If you still see this issue post upgrade, check to see if the report being used is the Out of the Box (OOTB) report. If the issue is not happening with the OOTB report, the custom report may also need to be updated.