External output displaying on Screen

For some reason, whenever I activate the program output to external display, it generates a small winde=ow and out puts on main screen, bypassing the external display. Did not do this before update.

Strange. Is it possible to delete the output-destination and to add it again? Does this solve it?

@camsna I think this is caused by the external screen being in macOS full screen mode. Can you please check if that is the case?