Try reproducing it very simply. Create a job that is not multiinstance that is very simple and is not multiinstance. Export it, delete the original job and re-import it. Is it now multiinstance?
no i don't succeed to reproduce it.
Apparently it's specific of my project. I exprot and import datatsage between 2 environments which are not (certainly) the same.
If your project isn't broken (a DS.TOOLS REINDEX and clean up doesn't change the problem) then I think you need so submit this to Ascential support, since we won't be able to reproduce it either. Please remember to post a solution so that others may profit from your thread.