Enumeration Data Types disappearing from Mass Editing View

I’m working on requirements for a project, through the Requirements Viewpoint, and I’m having the following issue:

When sending a Requirement in Mass Editing Viewpoint I can set the Enumeration Data Types which I have created together with additional ones already existing:

If I try to send a second requirement in the same Mass Editing, my Enumeration Data Types disappear:

And I can’t even add them through “Select Columns”, by right clicking on one random column, since they’re not available.

How can I keep my Types? I’d like to edit all the requirements which I’m creating in the same Mass Editing View (as in the figure, but with my Enumeration Data Types too).

Thank you in advance,