Solved 
The problem was with the translation tool. It seems that we started some submissions with only one language. And then we added a second language. And even if we fill all the metadatas in the contribution forms, the metadatas that can be translated were not present in the exports (CorssRef and G. Scholar).
Solution : Do not add a language once submissions is in progress.
be aware : the fields concerning affiliation will not be present in the CrossRef export, even if you have provided RORid. cf. does-the-crossref-export-plugin-include-affiliation