iPhone 8 photos corrupted on PC, fine on phone

Please be more specific. I presume the "PC" is using some Windows version, which one? Does it support .heic?

Do you have the iPhone > Settings > Apps > iPhone to automatically convert .heic to .jpg? In my experience that might in some workflows import as .jpg extension but the image itself is still HEIF which Windows version without .heic support does not open and might complain that it is corrupted.

Not that it matters much but also describe how you import. Via File Explorer and right-clicking the iPhone > More options > import > etc, or via Windows Photos application?

The iPhone keeps thumbnail and preview copies of pictures to help speed up scanning and viewing of pictures. But the original picture file could be corrupt, since you're not using that to view the image. The test is if you can Edit the picture-- it requires a functioning original to do that. Can you edit the pictures on the phone that have been labeled as corrupted?

If the original pictures files are corrupted, then you may have to rely on your backup files to recover them.

You did not say if you are using iCloud Photos-- that might be another option for saving the pictures.

Windows 11 Home or Pro? It seems Pro has .heic support built-in.

You didn't answer which Photos transfer setting is used in the iPhone.

Is the iPhone Camera set to shoot .heic or .jpg? Are the imported images .jpg or .heic? If .jpg, does it matter if you change the extension to .heic?