Si this is quite curious : I have a Field Group named "Médias-Photos-Fields" set to be used on Post Types "media-photos". But ever since I returned on this site to make sure Oxygen Builder update to 4.0 was working fine, I realised this problem : the field group's fields appear on the page of the Field Group. What I mean is : while I try to modify (or simply update) the page where the Field Group has been created (MB > Custom Fields > Field Group > Fields/Settings page), it is not possible since the fields appear at the bottom of the page, as if they needed to be filled in ! But it makes no sense since they should only appear of a custom post page, not in the page used to create them ! I think a screenshot will make you understand what I mean.
And this happens on every page of every Field Group : the fields are shown at the bottom, and require to be filled in or refuses to save the page ! Therefore no way to change anything !!! What is this ?