Meta description: FB works, twitter not

Hi there, I started to use different meta titles/descriptions for Facebook and twitter. For my first post it works for Facebook but not for twitter, although I can see the different titles/descriptions in the source code. Look here:

http://kmeducationhub.de/melbourne-knowledge-management-leadership-forum-201511/

I’m using twitterfeed.com to auto-post my posts to twitter and facebook, where post content is title&description. But that should not be the issue. Maybe it’s because I use symbols like @mention or #hashtag in the twitter title? Or maybe it has s.th. do do with the twitter card I’m using?

Sunny greetings from Germany
Boris

https://wordpress.org/plugins/wordpress-seo/