My issue concerns broken featured images in excerpts on category/archive pages.
The problem was first much more extensive, concerning all featured images and even images in single posts. Most of these problems were, however, solved when installing the plugin "responsive images". As advised by Graphene developers.
I am using custom uploads path. My media settings differ from default: Thumbnail size (155*155), medium size (220*122) and large (1280*720).
The problem looks as below:
I will be grateful for any help/advice you guys can provide.