Recover files from a "working" external hard drive

Solution 1:

Your files are corrupted.

If you can use macOS or Windows to open these files, you’ve reduced the points of failure that would have caused it. You’re down to the USB enclosure or the drive itself.

Recovery software won’t work because it looks for “orphaned” blocks of data. When you have a file, nothing is orphaned. The software has no idea that the contents are a jumbled mess, it just knows the file is complete.

For now, test out your drive. Write files to it. Then disconnect it, reconnect it and try to read those files back. If it fails, your enclosure and/or drive is failing.