Featured images on posts module not appearing (perhaps due to appended filename?)

I am having an issue with the featured image for blog posts not appearing in the posts module, even though it does appear on the individual post page. I inspected the code to try and find the cause, and the image URL for the thumbnail images that are not appearing are appended with image dimensions, eg “filename-1024x380.jpg”, when the actual filename is “filename.jpg”, and on the post page it is correctly referenced in the code as “filename.jpg” and thus appears. Actual files with the dimensions appended to the filename do not appear to exist in the wp media library or anywhere else. Any ideas why this is happening and how to fix? Thanks!