Thumbnails distorted on mobile only

I was having trouble with the thumbnails in my slider appearing distorted/stretched, and eventually some tweaking to the settings made the thumbnails work perfectly on desktop.

Now, I am having the issue that the desktop thumbnails look great, but on mobile they are stretched out of proportion.

Reading a few other forum posts, I went back to the settings to remove the automatic cropping and resizing, but this just made the desktop thumbnails distorted again. Has anyone else experienced this and found a mobile fix?

Thanks!

The page I need help with: [log in to see the link]