Hi Andy,
Thank you for your reply.
As it turned out it was not fixable by css anyway. It appears to be an issue in WooCommerce. The one side says it’s a bug WooCommerce says that this hook is especially for showing the gallery thumbs and should be left alone for anything else…. Weird, because WooCommerce is propagating the flexible layout option with their hooks.
None the less was someone over at stackoverflow.com very helpful to provide me with the solution. As a matter of fact the outputted data of the description tabs is not “lost” it is still in the DOM. Just a tiny piece of javascript makes it visible again. Someone at stackoverflow.com helped me out with it.
Anyway, as always, thank you for the effort to help me out.