We investigated the issue and found a bug that is causing the incorrect deflection check in this case. This has been logged with id# 460624 and will be fixed in the release of STAAD.Pro SS6 SP3 coming out at the end of June 2016.
As a temporary workaround, for the second set of design in your file dealing with serviceability, you may use the CODE AISC instead of the CODE AISC UNIFIED which would invoke the AISC 9th edition code for checking the deflection. As far as deflection checking is concerned, it should be the same for both codes. However we are getting the issue addressed in the AISC 360 UNIFIED code with top priority.
As a temporary workaround, for the second set of design in your file dealing with serviceability, you may use the CODE AISC instead of the CODE AISC UNIFIED which would invoke the AISC 9th edition code for checking the deflection. As far as deflection checking is concerned, it should be the same for both codes. However we are getting the issue addressed in the AISC 360 UNIFIED code with top priority.