If you are using this GroupboxHelperWidget widget the documentation states:

The order in which to put the elements in the group box:

• The element to put in the header, usually an individual element or a table
• This widget
• Other elements, which will remain in the group box body.

So looking at your screenshot you need to place the table first and the widget second IN the groupbox. 

Already answered here: https://forum.mendix.com/link/questions/105759

GroupBOX help required – not working expected as shown below

Mendix Forum - Questions (mendixcloud.com)

ANY SUGGESTIONS??