vertical images get cropped when post is published

Hi,

For my posts I often use vertical photos (i.e. higher than they are wide). In de post editor it all looks normal (as does it when you click on a photo in a post), but in the actual post itself, vertical images somehow get cropped and the balance of the photo is off.

Even when I click ‘full size’ for the image, it gets cropped in the post.

Does anyone know how I can fix this?

Here’s a link to a post where this happens: https://pieinthesky.nl/travel/australia/things-to-do-blue-mountains/ (fourth photo in the post)

Thanks in advance!