I just found out, that the autoplay setting has no effect on youtube videos anymore. No matter if 0 or 1 is passed to the parameter, it keeps starting it. In the API reference i couldn't find anything but on internet some people using "0" instead of 0 and some using ?autoplay instead of &autoplay..... nothing worked for me. The only way to stop it to autoplay by default was to remove the parameter (&autoplay=#autoplay#) from the "defines" in /modules/boonex/videos/classes/BxVideosConfig.php
I can reproduce on demo.boonex.com