You or Podpage has shared a link to your episode on social media and the images are not showing (or the incorrect image is showing).
Here is how to test this:
Go to Pages > Episodes > Episode List and edit the episode with the image issue
Scroll to the bottom to ensure there is a share image in place
Go to https://metatags.io and put in the link to that episode and click Parse Meta Data
If the images appear, Podpage is sending the correct information and the issue is with the social site.