NX-NASTRAN doesn't allow enforced displacements to be scaled in linear load case combinations, however, no warning or error message is displayed in FEMAP. It is possible that such a warning is issued in the F06 or something but I think that isn't obvious enough. We need a warning in the messages window that says something like "Enforced displacements included in loadcase XXX are not scaled. A factor of 1.0 is applied." when the load factor is <> 1.
Nastran does not support scaling enforced displacements. Your best option would be to run the enforced displacement condition as a separate subcase, run the other loads as a second subcase. You can then use Femap to scale and combine the results outside of Nastran.
In Femap you can find this under Model/Output/Process/Linear Combination