Content Sites – White Edit Space

hi there, i updatet today to adventurous pro and wp 4.5, and when i now go to the edit mode of a site the content area displays white - when i mark the content it is visible... how can i solve that issue? i want to show the customer how to edit sites on his own, but when he only sees white content area this is hardly to manage for him. when i change themes to a standard one, the content area is as it should be, so i wonder if there is a bug in the adventurouspro_3.6 file? thanks for your answer, jochen