If you have Dark mode switched off for your project and you use a custom image, it still tries to display the dark mode image on preview when the System it set to Dark mode 😵💫 Video of the bug in action…
https://share.cleanshot.com/3xLblfYQ
Reported on the forum: https://forums.realmacsoftware.com/t/image-not-displaying-with-custom-source-url/54641