In my theme's archive template, I'm using
to get a specific thumbnail size for each post. But that doen's work on all posts. Some posts display their featured image in full size, while others display the correct "list-thumb-small" size.
I have set the custom image size in functions.php:
add_image_size( 'list-thumb-small', 225, 185, true );
Why is this happening and how can I fix it?