V6 - Forms - Display Reference as "Checkbox List" -issue

Hi Support,

Seems my last posts weren't imported in new forum platform..but is ok...the new Forum is awesome...
So I repost again:

In FORMS when I have a drop down with reference atytributes is ok, all the referernces are shown:

BUT, when switch to "Checkbox list" only one record is shown:

thank you

Can anyone confirm/test this?
I'm doing something wrong or it's a bug?
Thank you.

Is your reference single or multiple? Checkbox lists are supposed to be used for multiple references only