We have one customer who is using Windows Server 2012R2 as print server with Win10 clients. For unknown reasons the print jobs which are created by Win10 apps like Edge or Foto Viewer are stored in XPS format at the spool directory (or at least I think that it is XPS format, because if you open the file as a zip it has a pretty similar structure). The file names are the same as usual (e.g. C:\Windows\System32\spool\PRINTERS\00002.SPL). We need to analyse the PJL header of the print jobs and so XPS format is a problem.
I tried the replicate the same environment but I didn't managed to reproduce this behaviour. And so I'm searching for the setting, that causes this.