Well, good luck with the ticket and do keep us up to date on what it is. The galaxy and web site installers should be exactly the same product according to GOG, so if there is some difference it would be good to know.

Speaking of which, I was just in a thread discussing that. Apparently, some games have some differences between versions based on their installer. The game Riven on the downloaded-files installer was a CD version, 1.00, while the GoG Galaxy version was a DVD version, 1.10. The difference there is in how the FMV video is compressed, which produces some noticeable changes. This wasn't the only game with reported issues, according to some in that thread.
https://www.gog.com/forum/general/riven_downloaded_from_website_is_inferior_version_compared_to_galaxy_download/page1
I've corrected that post to remove it, thanks. Even though it's a five-year old Dell OEM, I'm not interested in having others access the order information from the Dell website.

Regarding admin priviledges, that was in reference to issues I've had previously with rights management on files and folders. Basically, around the time of the Windows 7 update, there was a major change to how the system organized its pathways (folders? Just a lot of "dummy" folders from the XP era such as a non-existant Documents and Folders being replaced with a Documents Library), and somehow this screwed up my user profile to the point that it had no access to any files or folders. It was a pain, but I managed to restore all priviledges to the user profile through manually adding my user account to all files and folders in the security options.

Yes, that is why any difference is interesting, the installers should be the same.