Thanks for the fast response JessicoChan!
I did some experimenting and I wonder if the image sizes weren't too big. The file sizes were okay, but the images themselves were very large. I opened up some new projects with smaller textures and props and it stopped the issue from occuring.
Another thing that may have happened is that the images I originally used were saved within a Cloud folder. Not sure how EFPSE works, but might any Cloud desyncs down the line caused an issue? I know I suffered a couple.
Thanks for the help. I had a feeling this was to do with the images as they were the first thing I experimented with.