Title tells the story more or less... after having played all day yesterday, I found that GOG Galaxy was seemingly downloading the complete game a second time when I stopped playing, the complete 105 GB. After reading about the hotfix I was a littlebit surprised that it takes the complete 105 GB again, but whatever. Let GOG Galaxy finish and install, just wanted to start the game and was informed about a corrupted file by the launcher. Checking the alteredFiles.txt as suggested in the support article I found following information:

Version: 4.1.1.3624901
Platform: galaxy

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Altered/Added files 1
D3Dcompiler_47.dll

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Files in Mods folder 0

I run a google as well as a windows search for D3Dcompiler_47.dll. It seemingly is a DirectX component that the windows search detected in several different places and for several different programms on my computer, four times in the BG3 folder alone. One of the files was from the original download on 03.08, the other three have been changed during the patch this morning.

I run check / repair installation in GOG Galaxy, which led to another 175 MB being downloaded, however the error message still pops up and none of the four D3Dcompiler_47.dll files in the BG folder has been updated.

Any idea what I could try next would be very appreciated... I really dont want to download everything a third time. Could I just ignore it, since this seems to be DirectX realated and I am using Vulcan anyways?

Thanks mate, good idea, I'll give it a try.
That did the trick... thanks a lot!