timppu: I don't think I saw that Earth 2140 manual error that SirPlatform has been reporting. However, I now had a problem with these two files:
setup_system_shock_enhanced_2.1.0.4.exe
patch_witcher3_1.01-1.10_2.0.0.40.exe
Verification would list them as corrupted, with both the md5 sum and the file size being wrong. I tried to check their digital signature but the whole tab was missing from their properties (in Windows), I guess that already indicates they were not downloaded properly.
Anyway, when I performed the download again, they would still be wrong. New download tries would always consider those two files faulty (wrong size, I guess), and try to download them again.
In the end, when I removed those two files manually from my GOG collection and then redownloaded them, after that they seemed to be ok and it wouldn't try to download them again. I didn't yet run another verification for them.
Any idea what went wrong there? If the script redownloads some files, doesn't it remove the original corrupted file first? Why did I need to remove the faulty files first, before trying a redownload?
I ran the script in Linux Mint, and downloading directly to a NTFS-formatted external hard drive.
(Sorry if this issue was clarified earlier already, it is a bit hard to follow some of the error reports in this discussion.)
By the way, SirPlatform is my brother. I'm SirPrimalform, the one without the beard. It's ok, people often confuse us.