QToolbutton with popup mode QToolButton::InstantPopup and a stylesshet have 2 arrows.

The normal arrow, and a big arrow drown in the center of the button

.

 It's the same problem of QTBUG-98286. Perhaps the patch done to correct this bug have introduce this one.

QToolbutton with QToolButton::MenuButtonPopup also have the problem + the menu part seems always highlighted

with stylesheet: — without:

qApp->setStyleSheet("QMenu::item:selected { color: white; }");
QToolButton* tb = new QToolButton;
QMenu* mnu = new QMenu(tb);
tb->setMenu(mnu);
tb->setPopupMode(QToolButton::InstantPopup);
tb->show();