I did try to edit a submission I have in queue that I added a link to a photo to a few days ago, just to see if I could replicate, and I could. It’s an image I uploaded to my Imgur account, which I haven’t had issues with in the past (just a screenshot from Street View).
I tried removing the g in .png, adding it back and putting in a space after, and received the error. I’m using a Windows 11 laptop and Google Chrome, but being it’s happending to others on multiple OSs and browers, it does appear to be more of an issue with the Wayfarer website.