Well, if you got your stash files the same way from the same source, then I wouldn't be surprised that they don't work either. The image that worked before, if you try to download it again, the exact same way as with these images, does it still work?

Redownload the same file I've linked up, still brings out an error in Paint.NET and Paint SAI.

I really don't understand why those images from that wiki suffers this.

And this is the file from Rocket Knight Wiki that you said was working before?

The Rocket Knight Wiki images have no problem, the files I've mentioned in the previous post is from the Rayman and Claus' Skylanders Fanon Wiki.

For the ones that work, are you downloading them the exact same way as the ones that don't (browser, drag vs. right-click, etc.)? I tried the dragging method on my Windows 10 using Edge and it saves as a WEBP when I do that. Perhaps that is what you are getting.

I download the images from the Rocket Knight Wiki via "right-click and save image as" cause dragging it, will result the HTML document.

Okay. And if you download the images from Skylanders Fanon wiki using the right-click, what happens?

When downloading the image from the Rayman and Claus' Skylanders Fanon Wiki through right-click, It still happens that the image has that error in Paint.NEt and Paint SAI.

That is interesting. What browser are you using and have you tried a different browser?

The same browser I use, Google Chrome.