We prepared a hotfix for you which I am attaching to this post. Please check if everything works fine and let us know.
The issue with editing MediaPlayer's theme in Blend turned out to be weird and you should use a temporary workaround until we have time to properly resolve it. Here is the workaround:
When you edit MediaPlayer's template in Blend start as you would normally do, but when Blend generates a copy of the style for you, find the following line:
and substitute it with this one:
The second line is the actual code in the control, but while generating a copy of the style, at run time Blend substitutes the trigger with the version on the first line.
We also found another issue with the themes which does not allow you to put themes/styles in the resources of your application (App.xaml). However, if you keep your custom styles/themes out of App.xaml there should be no problems. We will be investigating this further, but you should stick with the workaround until we resolve the problems.
Hope this solves your problems. Let us know how it goes.
the Telerik team
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