Workspace/MCstudy different for bin/unbin fit

Dear experts,

I want to produce some toy MC to check the stability of a fit. I have 6 data samples which are fitted simultaneously and the output of the fit is saved in a root file using the RooWorkspace.

Then, I open the root file, I read the pdfs and create a simultaneous pdf by adding the individual pdfs. I create a RooMCStudy with the simultaneous pdf, and then I generate and fit.

When I do a binned fit and I save in the root file workspace the pdf, no problem appears in the generation and fitting part, the 41 parameters of the fit are generated and fitted. The problem comes when the fit is done unbinned, when I read the workspace to generate and fit, only 26 variables appears which are the yields of the different pdf contributions, but no sign of mass peaks, sigmas or other parametrizations of the pdf.

I don’t know what can be the problem, as the code is the same, also I do not know if this is due to the workspace or mcstudy,