When I execute the setup I've been asked for Part 11, which is weird because there are only 6 files.
I've downloaded the setup and the 2 first parts a couple of month ago and today the last 4 parts, but all of them seems to be the same version so that should not be a problem

Any ideas beside having to download everything again?

Thanks in advance

Witcher 2 comes in 13 parts (see attached image).

Same problem. Used GOG downloader since file was so big, installer keeps asking for the 11th part. Manual download comes in 13 parts. Not sure what's going on, needs a fix.

The GOG downloader was always a bit wonky, even when it was still being maintained. At this point, it is effectively abandoned (in favor of the upcoming Galaxy), so do not hold your breath waiting for a fix. The only "fix" available is to download manually in the browser.

I still sent a support ticket to let GOG know it happened with a link to this post. Someone probably forgot to add a few of the parts to the download queue for Witcher 2.