On windows with a project on a file server there are two ways to open the project. One can use a “Mapped Drive” like “Z:” or the “UNC Path” like “//FileServer/…”.
If one opens a project on a file server using the UNC path everything works except the BOM generation. Kicad has no issue in creating the .xml file, however the supplied “xsltproc” program fails to create the .csv file. It doesn’t seem to support command line file path arguments in “UNC Path” format.
Just a heads up to other KiCad users. I suppose it’s technically an xsltproc bug/problem/issue.