Workflow problems after migration from 3.1.3 to 3.3.4

Hi,
I have an environment with Elsa + Elsa Studio and many workflows created with Elsa Studio.
Everything worked with no problem, but after the migration from Elsa 3.1.3 to 3.3.4 the workflows started to give some errors.
I've taken a look at the workflow instances and I noticed that the workflows used during the executions after the migrations were wrong (it seems an old version but I'm not sure).
After reopened in the designer, saved and published again, everything started to work as usual. I've done for all the workflow definitions.

Thanks in advance,
Andrea