Default Gallery thumbs blurry, other thumbs fine

Hello, I’ve only just started trying to use the default WP gallery again and the thumbs are extremely blurry. I’ve seen some references to resizing images, but I’m working with images I want people to be able to view full-size, and besides the thumbnails are crispy-clear, so I don’t understand why the gallery thumbs are so nerfed :/

Done quite a bit of searching w/ no answers, anybody out there have any real fixes or am I back to never using the thing?