Group box setFont() oddness

[Perdrix]

ui file:

    QGroupBox *registerAndStack;
    QVBoxLayout *verticalLayout_8;
    QFrame *frame_1;
    QVBoxLayout *verticalLayout_9;
    QLabel *openLights;
    QLabel *openDarks;
    QLabel *openFlats;
    QLabel *openDarkFlats;
    QLabel *openBias;

my code:

	QFont font(ui->registerAndStack->font());
	QFont bold{ font };
	bold.setWeight(QFont::Bold);

	ui->registerAndStack->setFont(bold);
	ui->frame_1->setFont(font);
	/*
	ui->openLights->setFont(font);
	ui->openDarks->setFont(font);
	ui->openFlats->setFont(font);
	ui->openDarkFlats->setFont(font);
	ui->openBias->setFont(font);

result:

I also tried setting the font on each QLabel with the same result. The non-indented QLabels all ended up bold even though I explicitly set the font non-bold. The only distinction about the non-bold lines is they have an explicit stylesheet set "margin-left: 30", while the bolded lines have no stylesheet.

Hmmmm... The plot thickens: I moved that code from the ctor to an mf (onInitDialog) that I call from showEvent, now that groupbox is displayed as I expected, but this one:

	ui->processing->setFont(bold);
	ui->openPicture->setFont(font);
	ui->copyPicture->setFont(font);
	ui->doStarMask->setFont(font);
	ui->savePicture->setFont(font);

still displays in bold, but this one:

	ui->options->setFont(bold);
	ui->settings->setFont(font);
	ui->ddpSettings->setFont(font);
	ui->loadSettings->setFont(font);
	ui->saveSettings->setFont(font);
	ui->recommendedSettings->setFont(font);

	ui->about->setFont(font);
	ui->help->setFont(font);

doesn't!!!

Additional data: the Options groupbox has a stylesheet: background-color: lightcyan, but the processing groupbox does not.

Baffled
David