Inconsistent look of QScrollBar on Windows

[Thinium]

I have a custom scroller which looks fine on Mac, but on Windows it has a strange gray background.

Here is a photo of the custom vertical scroller. The horizontal scroller is the default scroller, just for comparison:

Here is how it looks on Mac:

Here is my code for the custom scroller. Am I missing something in my stylesheet?

// in the MainWindow:
setStyleSheet( "QScrollBar:vertical { \
                  background:rgb(42, 42, 42); \
                  border-top-right-radius:2px; \
                  border-bottom-right-radius:2px; \
                  width:16px;\
                  margin:0px;\
                  }\
                  QScrollBar::handle:vertical { \
                  background-color:rgb(66, 66, 66); \
                  border-radius:4px; \
                  min-height:20px; \
                  margin:2px 4px 2px 4px;\
                  }\
                  QScrollBar::handle:vertical:hover, QScrollBar::handle:horizontal:hover{ \
                  background-color:rgb(42, 130, 218);\
                  }\
                  QScrollBar::add-line:vertical{ \
                  background:none;\
                  height:0px;\
                  subcontrol-position:right;\
                  subcontrol-origin:margin;\
                  }\
                  QScrollBar::sub-line:vertical {\
                  background:none;\
                  height:0px;\
                  subcontrol-position:left;\
                  subcontrol-origin:margin;\
                  }\
                  QScrollBar:left-arrow:horizontal, QScrollBar::right-arrow:horizontal {\
                      border: 2px solid grey;\
                      width: 3px;\
                      height: 3px;\
                      background: white;\
                  });

[Thinium]

Turns out that I needed to add also the arrow and page definition on Windows. For example:

QScrollBar:left-arrow:vertical, QScrollBar::right-arrow:vertical {
border: 2px solid grey;
width: 3px;
height: 3px;
background: white;
}

QScrollBar::add-page:vertical, QScrollBar::sub-page:vertical {
background: none;
}
This fixed my original issue, but the arrows aren't visible (which doesn't matter in my case, but it's just weird that they don't show up).