QSpinBox starts auto-incrementing after a few clicks

Clicking a QSpinBox or QDoubleSpinBox up/down buttons too quickly results in the spinbox continuously incrementing as if the button was pressed and held.  It does not stop until clicking a button again.  Even after moving the mouse away, it continues to increment. 

This makes the spinbox almost unusable as I commonly click several times in a row and each time I do this it starts counting out of control. 

Works OK under Qt 5.11.2

See attached video and simple main.cpp