There are multiple copies of the asset set now, and I have 3 of them checked out on my local machine. Vega Strike (specifically vssetup) is getting mixed up about which copy to use. The algorithm for determining the asset folder location, is not that smart.
Filing as part of https://github.com/vegastrike/Vega-Strike-Engine-Source/issues/98#issuecomment-626981181 on behalf of @stephengtuggy