EditNuissanceParameters' RemoveNP can't handle PiecewiseInterpolations
Besides FlexibleInterpVars (usually used for overall syst.) in typical histfactory based workspaces one also finds PiecewiseInterpolations. The RemoveNP operations current do not seem to handle those. Hence, when removing a NP from a workspace it is only removed from FlexibleInterpVars as well as its constraints are removed. If the parameter in question, however, is also part of, e.g., a PiecewiseInterpolation one ends up with an essentially unconstrained parameter that could subtly or significantly affect the results.