My apologies, as I am sure this has been discussed. But, owning offline backups is super important to me. I have been downloading them through GOG Galaxy and saving them all to a drive. However, recently I noticed the backups through the website are sometimes different, or that backups on Galaxy will not work and I'll have to download them through the website.

What I am getting at is, are the backups on GOG Galaxy true offline backups? If so, why is the app so divisive?

Edits: Clarity.

Offline installers in a browser are displayed as multiple 4 GB pieces, while GOG Galaxy shows a single item and the total size. The downloaded files are the same.

The fact that you claim there's some sort of difference (file size maybe?) and the installers don't work suggests failed downloads. It's also worth inspecting the drive where you're storing these files using chkdsk and CrystalDiskInfo.
Since you have a sizeable collection, you may want to use a tool like Gogg to backup your collection and hash the downloads to ensure integrity.

Yeah, some of the installers have not worked. Something else may be amiss. This is great advice, thank you. I'll definitely download Gogg as well.

I see you've discovered GOGPlus Download Checker. I don't know if the issues you're having with it are because it was last updated in 2022, or because of the recent server hiccups. I suppose you'll find out in the other thread; the author of the program is pretty active on the forum.

You're welcome. Best of luck getting this sorted.

Yeah, thank you! I'll figure it out, even if I just have to end up re-downloading everything.