A QOpenGLWidget is placed in a QScrollArea.
This ScrollArea is put in a QGridLayout with 3 other QOpenGLWidget.
The drawing of the first QOpenGLWidget overtake the other QOpenGLWidget.

I have made a little exemple that can be found in attachement.
The QOpenGLWidget that is in the QScrollArea is clear in red, the other have no paint function.
Moving the scrollBar, move the red rectangle in the other QOpenGLWidget.
The result can be found in the picture in attachment.