Hm, I'm not sure why but it seems like decoding the webp is the actual problem. The only thing I can think of is that windows 8 somehow uses a different codex.
Your best bet is to use a different operating system to see if that works. You could always download VMWare and then download Ubuntu 20.04 and then run it as a virtual machine. Then you can download FET and try it there. But this is a LOT of trouble to go through, man. I remember being able to just click "Ignore this" and everything worked fine.