FeatureTooltip widget version 3.1

Hi,

A user pointed out to me that the tooltip doesn't display for some parcel.
What could be the problem ?
I have traced "toolTip" ligne 110 and informations are in !
I don't understand!
Is that it could be in the MXD, an option that prevents the opening of the tooltip ?
I don't know where looking for!

Thanks for help!

EDIT: The popup doesn't display either for this parcels ...