Version 1.8.5 works, but not with the dash formats...

About: Download YouTube Videos as MP4
I have line 39 in your script changed to:
When I click on the buttons for downloading the dash formats, they lead me to a new page in witch only the video or audio is playing. I am able to right-click and save them in order to mux them together with ffmpeg.
This is rather inconvenient...

I have mailed you the debug info.