ZDoom

I've never had this happen when I was still using my GOG installation of SW.
Is this something exclusive to Linux?
I can't do anything here as I cannot reproduce this.
In any case, I'd strongly recommend not to run these games from those dirty installations - it's really better to copy the GRPs to some safer location because it massively reduces the risk of loading unwanted garbage content.

Irrespective of it loading SW.grp fom the Twin Dragon folder, it is actually a problem as such? The only main issue I see here is content in Raze's directory should always override a search path, unless the search path is higher than Raze's path listing for $PROGDIR in your INI file.

Hmm, this happens with Duke Nukem 3D Megaton Edition from Steam as well; The duke3d.grp inside the "classic" folder is randomly loaded instead of the one in the working directory.

Reminds me of this one: viewtopic.php?f=341&t=72115

These packages surely come without any consideration for how to set up their data.
I'm afraid, but I do not have a quick solution here, it may be best to move that folder elsewhere if it causes interference.

I have Shadow Warrior Classic Complete on GOG.com, and the Linux installer puts the Twin Dragon files into the "dragon" subdirectory of the main game data directory. When I run Raze from the main game data directory, it sometimes loads Sw.grp from the "dragon" subdirectory, even if I don't want it to do so.