Mori_Yuki: I hoped that they would at least investigate whether there is a problem, and if there is, ...
neumi5694: Who says they didn't?
Some times finding a problem takes longer than half a day.
They might, I'm just not expecting it. Otherwise, support could have communicated this to me, instead of offering a generic list of possible fixes - most of which have to do with Galaxy (deactivating TLS 1.0, etc.) and not the offline installer.
neumi5694: Personally (just a shot out of the blue judging previous posts) I think it's the SSD overheating by the sheer number of single files to be written.
I can rule this out for my system; temperatures remain low during installation. The problem, in my case, already starts when the process initiates, and the installer window can't be moved. This suggests to me that it isn't the system at fault; otherwise, logs and apps I used to monitor the installation might have shown something suspicious. Nothing gets blocked, the main installation folder is called .\GOG\GoW, the drive does not contain non-English letters (something I read could also cause problems with GoW installation), and nothing gets blocked or constantly uploaded to analyze files for viruses and malware. There is really nothing else I could think of to make sure that it isn't my system at fault.
SSD/NVME can cause the problem; the number of small files can massively slow it down, which doesn't seem to be a universal problem, and BSOD can be caused by any number of other problems and only coincide with the installation.
I'm not going to wait until they eventually start investigating the offline installer and find a solution for the problem when - based on replies to my posts - it doesn't seem likely that GOG sees something wrong with it, and Galaxy can be used to install it - if only for this once. As long as there are offline installers, I expect them to work, and the installation to finish in a matter of minutes. I just don't have high hopes, and that's why I decided to refund instead of waiting.