Unexpected change in QGridLayout spacing when showing/hiding widgets

In the attached, when I change the selected combobox item from "line edit 2" to "line edit 3" and back again, the vertical spacing between the widgets disappears, but reappears when I reselect "line edit 3".

In widget.cpp, if I comment out either of "vComboBoxLowerLeft->setVisible(false);" or "gridLayout->addWidget( vComboBoxLowerLeft, 1, 0 );", then I do not see the spacing change.

P.S. I can also make the spacing behave as expected if the widgets are in columns 0 and 2 instead of columns 0 and 1.