Corruption on AI upscaled videos - why?

I have lots of AI upscaled videos, but there is often a problem when it comes to people's faces, which is that when the face is small, the image that is shown is corrupted, or it is "crumpled", like all the elements in a person's face breaks down/falls apart.

I don't even know how to describe it better than that, but it is clear to anyone who watches such videos.

I am not a technical person and I have no idea about making a video or what goes into upscaling. But something clearly is not working with the AI technology that is being used to carry out these upscales.

This problem doesn't appear in every video though, but I estimate it appears in around 90% or more of the videos I have seen and I have hundreds of upscaled videos.

I have seen poor upscaling and also, upscaling that has been overdone, with the result that people looking like a cartoon characters.

Do you have an idea why this problem occurs and whether it can be fixed?

What AI are you using to upscale? Also, are you trying to reduce noise or actually increase it, from say, 480p to 1080p?

I am not doing any upscaling. I have no idea how to do this.

I am just watching these videos, nothing more.