date, user and group displayer doesn't work in preview mode and export: "Unknown display mode"

Hello,
For my Xwiki application, I created my Class (with string, date, 'List of Users' and Group properties), a Sheet and Template.
My fields are displayed correctly in view/edit mode except if I export my page and on preview mode.
In PDF/ODT export file, I obtain "Unknown display mode." instead of the value for all 'date' and 'List of Users' field.

For Group type it is worst because in view mode it doesn't work (I open a new issue)

Thxs.