Hirako__: You should definitely report this to the support (if you have the time) and they will (hopefully) fix it. Here the chances are much(much) smaller to be seen and fixed!
Thank you for your answer, and sorry for my little late one ; i was checking a few other things out of gog...
Yes, not sure how to do that and where on their site (website game page, app if there is an option for that ?), but i will try i guess... Actually i vaguely hoped they had some moderators on the forum able to report the thing, or a direct support intervention confirming that had been noticed.
As i said, 'my problem' there is solved (anyways) as i added manually the missing file (from the website), the game is now installed (from the offline pack, working now), but, yeah, could be useful for others if that could be fixed, i guess, or at least for the next full pack to be secured and verified...and the same for the other similar big install files for other games.
crossing fingers,
cheers!