Featured images on post site won't render since update.

Hi I'm running the Fotografie theme v.1.4.3 on Wordpress v.4.9. Since the theme update the featured image thumbnails for the post site won't render anymore. They get displayed in full size (height). Example: http://www.ninazimmermann.com The last entry from the 22nd of November stretches. All entries before rendered automatically. This appears in full width view only. In the vertical iPad view it renders as usual in a square shape. Did I miss a new setting or is it a bug? I have a couple new posts in the pipeline, but this issue destroys the landing page design. Help is highly appreciated. Thank you! Nina