Hi
I found an incompatibility with “shortcodes ultimate” plugin, I first reported to them at https://wordpress.org/support/topic/nested-su_spoiler/
When you have an ‘su_vimeo’ inside an ‘su_spoiler’ and the spoiler is closed when you click in the area occupied (but not visible) by the video, the video catches the mouse click.
This happens the same with ‘su_youtube’ and the ‘su_spoiler’ can be inside or not an ‘su_accordion’. I experimented with several themes.
I followed the steps they recommended (btw, the same you recommend), so I disabled everything (all of them) and switched to the default theme, the problem disappeared. This is a test site so this is no problem.
I switched back to you theme and GP plugin, the problem was present again.
Again, I disabled GP Premium and left GeneratePress theme, problem was present.
I can give you admin access to this site, so you see for yourself.
I am leaving it now with 0 plugins but Shortcodes Ultimate and GeneratePress theme.
Just load the page and click just under the closed spoiler at the bottom of the page, the video will start playing.
Thanks
Alain