WordPress is creating multiple copies of images

I am setting up a WordPress multisite and noticed that there are numerous copies of my images in the folder after uploading one. The new images are renamed (a number prepended to the filename) and then Smushed to create multiple file sizes.

I literally have HUNDREDS of copies of the same image in different sizes, with different names. Any idea on what is causing this to happen? I have tried deleting the images, I have even deleted them from the server, but more keep showing up. The strange thing is, it's only happening with one file - the one I am using on the homepage.

I am using Upfront builder to create a custom theme to be used across all sites on the network.