QSpinBox spin;
spin.show();
spin.resize(100, 6);

and lower heights print:

QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::setPen: Painter not active
QPainter::setBrush: Painter not active
QPainter::setRenderHint: Painter must be active to set rendering hints

I experience this while using a QPropertyAnimation to resize a widget until it’s gone.
This is the only style (tested Adwaita, Oxygen and Windows on Linux so far) and widget combination that produces warnings so far.