Hi Johan Visser,
Ribbon merging from a Page to a RibbonWindow isn't supported because a WPF Page can only have a Window or Frame as its parent. In our case, the DocumentContainer tries to host the Page, causing the following error:
System.InvalidOperationException: 'Page can have only Window or Frame as parent.'
We recommend you use a UserControl instead of a Page, as shown in our documentation:
Documentation:
Let us know if you need any further assistance.
Regards,
Sekar Sivalingam