Almost sorry to hear that 😉 No, I am not… I did set the image sizes to 500×700, 500×700 and 200×200, with hard crop, I also tried a few variants. And I got the above mentioned error on single product view. When the thumbnails were OK, I could not see the product in full size – on most products.
I am starting to think there have been to much trial and error in my WP installation, do you have any recommendation for backing up and moving a WooCommerce installation? The only thing of value is in fact my WooCommerce data, so it would be good if I could reinstall everything else.