Twitter Card sometimes does not display description correctly


#1

Our Twitter Card sometimes works fine and sometimes not. I looked at the metatags, but a can’t see where the difference is:

https://twitter.com/ariva, 8 Aug
This is not correctly displayed. Instead of the description in the metatag the description of the site which we used to create the Twitter Card is shown:
http://www.ariva.de/news/ROUNDUP-Milliardaer-Slim-funkt-O2-dazwischen-und-will-E-Plus-Mutter-KPN-schlucken-4743425?compr=0

https://twitter.com/ariva, 7 Aug
This is ok:
http://www.ariva.de/news/Commerzbank-sieht-Hoffnungsschimmer-bei-Schiffskrediten-4742202?compr=0

I don’t know what’s wrong, for me it looks fine.


#2

I need help, please!

This Link is ok and shows the right Twitter Card:
http://www.ariva.de/news/ROUNDUP-Eurozone-beendet-Rezession-Wirtschaft-waechst-staerker-als-erwartet-4747481

This Link does not, although it is displayed correctly in the validator:
http://www.ariva.de/news/Allianz-Sachversicherungen-koennten-nach-juengsten-Unwettern-teurer-werden-4747630

Is it possible to delete the Twitter Card and set it up again? May be this would help.