I'm not sure whether you have a custom control class library where you inherit from RadOutlookBarItem /RadRibbontab or you have a custom style in your project where you have customized our default control style. For the first case - since you have predefined the default control template in your Generic.xaml - you are losing the theming which is expected i.e. he new template will be applied to all themes. Please see attachment (the predefined Red Background will be applied to the RadOutlookBarItem no matter of the theme).
In case you have custom style and you switch themes runtime - please make sure that this style gets added to your application's merged dictionaries everytime you are switching the theme. You might check our documentation article where this is explained (here's
a link to it).
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