German Syberia issue has been fixed with todays update.

And you are mentioned in the changelog,nice.
Still waiting to see if the fixes show up for games i mentioned.
Btw support changed one day on here. And i didn't need it really anymore, but how does it work now if i would want to reach support for Gurumin, but like i said i am currently waiting to see if mastiff does anything about it, since EnforcerSunWoo contacted them.
Don't know if anyone contacted GOG support after the issue was found out.
And Flatout 1 don't have anymore info on it now.
All other games i tried from my library that i installed really worked without problems though, so no need for support.
Few of them were a little crashy like morrowind(with two patch mods), mafia (don't know it doesn't crash often i fully beat the game including extreme freeride and wanted to have fun in freeride but then on the countryside i crashed in a car and the game crashed so i unistalled it) and return to castle wolfenstein (also doesn't crash often). But these games aren't missing files i believe, it's just the nature of the games.

Just want to say that Gurumin is fixed now, at least an update showed up and it mentions the fix that also fixes the ending credits game crash.

Another case of missing files this time it's from December 16, 2014 found by montcer9012
https://www.gog.com/forum/general/missing_tutorial_executable_for_btcod_beyond_the_call_of_duty_commandos