I'm seeing a new binding error in the Output window with 2016 R3 that was not there before:
System.Windows.Data Warning: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='Telerik.Windows.Controls.RadRibbonView', AncestorLevel='1''. BindingExpression:Path=IsHostedInRibbonWindow; DataItem=null; target element is 'WindowTitle' (Name='WindowTitle'); target property is 'NoTarget' (type 'Object')
This is coming from the new MultiDataTrigger condition added to the WindowTitleStyle. It's also coming from the WindowTitle that exists in the RadRibbonWindowStyle control template, which does not have a RadRibbonView ancestor, as opposed to the one in the RadRibbonViewTemplate.