Images (thumbnails) disappeared

Hi there,

Since updating the plugin to the latest version, the thumbnails are not showing anymore. Here are some examples (scrol to the bottom of the page):

https://www.spierbouwers.nl/voeding/supplementen/top-3-supplementen-tegen-acne/
https://www.spierbouwers.nl/voeding/supplementen/levertraan-capsules-kopen/
https://www.spierbouwers.nl/voeding/voedingswaren/chiazaad-gezond-krachtig-en-superfood/

This problem occurs on all devices and browsers.

How can we fix this problem?