diff --git a/5.15.9/qtbase/src/plugins/styles/mac/qmacstyle_mac.mm b/5.15.9/qtbase/src/plugins/styles/mac/qmacstyle_mac.mm
index 86118b7..f674d7e 100644
--- a/5.15.9/qtbase/src/plugins/styles/mac/qmacstyle_mac.mm
+++ b/5.15.9/qtbase/src/plugins/styles/mac/qmacstyle_mac.mm
@@ -468,7 +468,11 @@ static bool setupSlider(NSSlider *slider, const QStyleOptionSlider *sl)
     if (sl->minimum >= sl->maximum)
         return false;
 
-    slider.frame = sl->rect.toCGRect();
+    // NSSlider seems to cache values based on tracking and the last layout of the
+    // NSView, resulting in incorrect knob rects that break the interaction with
+    // multiple sliders. So completely reinitialize the slider.
+    [slider initWithFrame:sl->rect.toCGRect()];
+
     slider.minValue = sl->minimum;
     slider.maxValue = sl->maximum;
     slider.intValue = sl->sliderPosition;
@@ -498,6 +502,14 @@ static bool setupSlider(NSSlider *slider, const QStyleOptionSlider *sl)
     // the cell for its metrics and to draw itself.
     [slider layoutSubtreeIfNeeded];
 
+    if (sl->state & QStyle::State_Sunken) {
+        const CGRect knobRect = [slider.cell knobRectFlipped:slider.isFlipped];
+        CGPoint pressPoint;
+        pressPoint.x = CGRectGetMidX(knobRect);
+        pressPoint.y = CGRectGetMidY(knobRect);
+        [slider.cell startTrackingAt:pressPoint inView:slider];
+    }
+
     return true;
 }
 
@@ -844,6 +856,8 @@ static QSize qt_aqua_get_known_size(QStyle::ContentsType ct, const QWidget *widg
             return ret;
     }
 
+    const bool isBigSurOrAbove = QOperatingSystemVersion::current() >= QOperatingSystemVersion::MacOSBigSur;
+
     if (ct == QStyle::CT_CustomBase && widg) {
 #if QT_CONFIG(pushbutton)
         if (qobject_cast<const QPushButton *>(widg))
@@ -1038,6 +1052,8 @@ static QSize qt_aqua_get_known_size(QStyle::ContentsType ct, const QWidget *widg
                     w = qt_mac_aqua_get_metric(HSliderHeight);
                     if (sld->tickPosition() != QSlider::NoTicks)
                         w += qt_mac_aqua_get_metric(HSliderTickHeight);
+                    else if (isBigSurOrAbove)
+                        w += 3;
                 } else {
                     w = qt_mac_aqua_get_metric(VSliderWidth);
                     if (sld->tickPosition() != QSlider::NoTicks)
diff --git a/5.15.9/qtbase/src/widgets/widgets/qslider.cpp b/5.15.9/qtbase/src/widgets/widgets/qslider.cpp
index bbfce61..5bf01d1 100644
--- a/5.15.9/qtbase/src/widgets/widgets/qslider.cpp
+++ b/5.15.9/qtbase/src/widgets/widgets/qslider.cpp
@@ -153,6 +153,13 @@ void QSlider::initStyleOption(QStyleOptionSlider *option) const
     option->pageStep = d->pageStep;
     if (d->orientation == Qt::Horizontal)
         option->state |= QStyle::State_Horizontal;
+
+    if (d->pressedControl) {
+        option->activeSubControls = d->pressedControl;
+        option->state |= QStyle::State_Sunken;
+    } else {
+        option->activeSubControls = d->hoverControl;
+    }
 }
 
 bool QSliderPrivate::updateHoverControl(const QPoint &pos)
@@ -315,12 +322,6 @@ void QSlider::paintEvent(QPaintEvent *)
     opt.subControls = QStyle::SC_SliderGroove | QStyle::SC_SliderHandle;
     if (d->tickPosition != NoTicks)
         opt.subControls |= QStyle::SC_SliderTickmarks;
-    if (d->pressedControl) {
-        opt.activeSubControls = d->pressedControl;
-        opt.state |= QStyle::State_Sunken;
-    } else {
-        opt.activeSubControls = d->hoverControl;
-    }
 
     style()->drawComplexControl(QStyle::CC_Slider, &opt, &p, this);
 }