Seemingly random binding errors for PopupBox

I seem to get this error at random times during the execution of my application:

System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='MaterialDesignThemes.Wpf.PopupBox', AncestorLevel='1''. BindingExpression:Path=Foreground; DataItem=null; target element is 'PackIcon' (Name=''); target property is 'Foreground' (type 'Brush')

It's not completely "random" as it seems to coincides with clicking on some UI element. The funny thing is, the element that is clicked on is typically NOT a PopupBox. Is anyone else seeing this? Is there perhaps an error in my code somewhere that I could trace this to and not a bug?

まず、説明されている UI 要素をクリックして報告された binding エラーを再現し、その後、メッセージで示されている PopupBox と PackIcon の binding 関係を調査します。完了条件は、エラーの発生元が toolkit かアプリケーションかを判断し、再現可能な原因または修正を文書化することです。