Self Hosted Video not playing

Hello at Kriesi,
and first of all thanks for the great theme once again.

I have (not the first time) integrated a self hosted .mp4 video in the fullscreen slider. This does not autoplay, I have to click on the slider 2 times to get it started. I have uploaded the webm and .ogv files in the same directory as the mp4.

In Edge browser it runs well. In Firefox not.

I have tried to:
– Add

# Video
AddType video/ogg                      ogv
AddType video/mp4                     mp4 m4v
AddType video/webm                   webm

to the .htacess file

– Deactivate all plugins.
– Integrating another self hosted video (see private content area) which works. So I guess it must be something with the webm video enconding.

Thanks for your help.

Best Regards