Hi, thanks for the reply.
I will try to simplify a bit my model before publishing it.
However making more trials give me few hints. The source of the issue may come from :
- parameters in vector form are not so well handle,
- records for parameter are not so well handle too. You need to expand the record when using it as a symbolical parameter
    Not working, keep in numerical form :
        WSMLinearize[model,Method -> {"SymbolicDerivative","SymbolicParameters" -> {"rec"}}]
    Seems to work :
        WSMLinearize[model,Method -> {"SymbolicDerivative","SymbolicParameters" -> {"rec.item1","rec.item2"}}]
- encapsulation of record (nested records)?

In addition the WSMLinearize function seems to be a bit unstable. Sometimes when using it, it fails, but when you re-run the function, it works.
Gilles