Featured Image being displayed at different sizes in blog posts

I recently noticed an issue with my site’s featured image on my blog posts. For some reason, some images are showing at a different resolution and I can’t figure out why since all images uploaded to my site are all the same size.

Here’s an example. This blog post shows a featured image that is slightly blurry even though the image uploaded is 1920×1277. If you right-click the image and “open in a new tab” (the image itself) you will see that the image being displayed is 1024×681. I understand that this size is due to my settings in WordPress being “Large Size=1024” but here’s the issue: Some blog posts display the image at it’s full size!

Here’s another blog post with a different image but the exact same size as the other (1920×1277). Again, if you open the image in a new tab you will see that the image being displayed this time is different: Now it’s displaying at it’s full size therefore not appearing as blurry to me.

Any idea what could be going on? I have verified multiple times that the images showing at a lower resolution exists in 1920×1277.

Here’s proof.