Several people draw plans in ArchiCAD and export them on the server, always in the same place using the automatic ArchiCAD Publisher. Someone creates the documentation in publisher with all the plans as PDF links that are constantly updated.
As soon as a PDF is linked in publisher, ArchiCAD can no longer overwrite it (file cannot be calculated).
This was never a problem in InDesign and ArchiCAD showed the same message if the PDF was open or someone had selected the PDF in the Finder.
So it looks like the publisher is "selecting" all PDFs links all the time.