x1    -2900
y1    490
x2    -2226
y2    961

I've single stepped into the constructor where I have:

QRect rctGeom(pParent->geometry());
rctGeom.setHeight(DataSets::mscuint16Height);
rctGeom.setWidth(DataSets::mscuint16Width);
if ( rctGeom.isValid() == true ) {
    setGeometry(rctGeom);
}

After setting the height and width the geometry contains:

x1    -2900
y1    410
x2    -2445
y2    949

mscuint16Height contains 540, mscuint16Width contains 456. I've single stepped onto the isValid call and it does return true which I find very odd given that both x1 and x2 are both negative. After calling setGeometry I see in the console:

QWindowsWindow::setGeometry: Unable to set geometry 480x540+-2900+410 on QWidgetWindow/'DataSetsClassWindow'. Resulting geometry:  486x540+-2900+410 (frame: 8, 31, 8, 8, custom margin: 0, 0, 0, 0, minimum size: 480x482, maximum size: 16777215x16777215).

Reading the documentation:
https://doc.qt.io/qt-5/qrect.html#isValid
It is certainly doing what it says on the documentation, but personally I think the logic needs and should be changed to validate if the geometry results in a non-visible rectangle as this does.

This is the logic it currently uses:

A valid rectangle has a left() <= right() and top() <= bottom().

I think it should be: A valid rectangle should be:

 right() - left() > 0 and top() - bottom() > 0  and
 left() <= right() and top() <= bottom()