Uploading comic page issue…

Hello,
I have been uploading comic pages no problem for a long time. But all of a sudden when I upload an image it says it wont be uploaded with the file extension (example) “comic.ext.jpg”
But when I look at the file in my finder, there isn’t a “.jpg” after the “.ext”. I don’t understand why it is suddenly doing this.

When I save the file in preview, I add the “.ext” at the end.
I have done it the same way for 20 pages and all of a sudden it’s acting up.
Please help!