Following line makes the ToggleButton thumb blurry (the circle that switches side when toggling the button.

<AdornerDecorator CacheMode="{Binding RelativeSource={RelativeSource Self}, Path=(wpf:ShadowAssist.CacheMode)}">

Link to line in source code

This binding on CacheMode seems at first hand also completely unnecessary, as this value can't be set in any way:

• The AdornerDecorator has no name
• The AdornerDecorator is inside the style template

The value will always be the default value of ShadowAssist.CacheMode, which seems to be following value new BitmapCache { EnableClearType = true, SnapsToDevicePixels = true }.

When I remove the CacheMode setting, the circle renders crisp and sharp.

With CacheMode set	Without CacheMode set