android design editor doesn't work with backwards compatibility enabled

Multi tool use
android design editor doesn't work with backwards compatibility enabled
So I created a project and when I added buttons and stuff to my activity_main.xml
they didn't show.
When I ran the app they where there but the design editor showed just a white screen with the black bar on the bottom.
activity_main.xml
So I tried some stuff and found out it works fine if I disable backward compatibility.
Is this a bug or how can I fix this?
I don't post any code because it doesn't even work with the templates you can choose when creating the project.
Thanks for answers!
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