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: