MultiPar VS HashCheck

but... depending on how much effort you want to spend fixing it I might be able to fix your current corrupt files, especially if the corrupt files are only mildly corrupt I could create a '.par2' file from mine (assuming you are on build 1436.28), then you would use MultiPar (i.e. https://github.com/Yutaka-Sawada/MultiPar/releases ) to scan your files and it will tell me how many blocks you need to fix it and then I could create recovery data with MultiPar. doing this might dramatically lower the amount of data I would have to upload as then you could use MultiPar which will fix your current corrupt files so they match mine identically.

MultiPar is the continuation for Windows https://github.com/Yutaka-Sawada/MultiPar

And this for Linux https://github.com/animetosho/par2cmdline-turbo

* MultiPar supports in-situ repair, which bypasses this problem entirely

To detect bitrot I use dynamix file integrity plugin, it compute Blake3 hash for each file, it is stored as extend attribute. You Can choose which share will be covered. For correction i then use par2 files using multipar https://hp.vector.co.jp/authors/VA021385/ https://github.com/Yutaka-Sawada/MultiPar (Windows only, par2cmdline for Linux. You could compile from source and add it to unraid if you want, i've done it for testing purpose)

And last but not less important - make regular parity files of your healthy important data, and store them somewhere. MultiPar is your best friend. Even if your data gets corrupt, with parity files you can restore it to it's former glory. Some limitations will apply, read the manual.

This is possible with MultiPar https://github.com/Yutaka-Sawada/MultiPar

More sanely, perhaps, get some M-Disc DVDs (if you can find real ones - apparently they're becoming just normal DVDs) and put one file on each, and then run https://github.com/Yutaka-Sawada/MultiPar on it to create parity files. Then store the file, the parity files, and the software you need (MultiPar) on the disc. To be safe, you probably also need to store the DVD burner you used to make it, as those are getting thin on the ground these days.

Note about par2: if one is using a windows system with a nvidia GPU this version of par2 is faster as it speaks CUDA.

For any file repairs use multipar, it's still being updated and has gpu acceleration. https://github.com/Yutaka-Sawada/MultiPar/releases

You can use HashCheck or similar (https://github.com/gurnec/HashCheck) to create hashes of your files and verify them. Periodically do this and if it ever fails, restore from one of the good backups.

Still better safe than sorry though, so I've been using TGRMN's ViceVersa Pro and sometimes Robocopy ever since. For easy checksum/hash gathering I use HashCheck Shell extension - but if you want to be a purist, the built-in certutil utility in modern Windows can get SHA-1 and other hash types .

Do you want to make sure it's the same file? GOG Games allows to "Verify that your collection matches" GOG Games here. To use, install Open Source HashCheck Shell Extension (old version) to compare against it.

That's good. In that case I would make at least TWO copies and verify those copies. I've been around long enough to see USB have random bit errors. I use ViceVersa Pro to copy and verify but that's overkill for your needs. You could also create a hash manifest with HashCheck Extension (Win) or the like, and diff the two manifests.

I use HashCheck: https://github.com/gurnec/HashCheck/releases/tag/v2.4.0

What I was suggesting is more subtle. There's an open source program called HashCheck https://github.com/gurnec/HashCheck I found that hooks into your Windows Explorer context menu to make viewing a checksum hash or generating a checksum file just 2-3 mouse clicks—it's actually pretty nifty as you can load the checksum file to check for data integrity across multiple files.

First verify you got from qbittorent.org and that the SHA256 matches. You can use certutil, powershell or https://github.com/gurnec/HashCheck

Not knowing how to hash check files https://github.com/gurnec/HashCheck