If you get The Fusion composition on the current frame or clip could not be processed successfully
, then a woking fix for me is
Go to Preference<User<Ui and uncheck the "Stop renders when a frame or clip cannot be processed".
After doing this DR was able to render the project. Also all effects etc. were visible and no frame was dropped. Nontheless if somebody knows it better or why this is a bad Idea, please feel free to lecture me.