We are not able to diagnose working files directly on the forum website. To help us evaluate, can you please email us your Stager scene and log file to Substance3d-bugs@adobe.com so we can investigate. If the file is under 20 MB you can attach it directly to the email. If it's larger, you can send via a file transfer link like Creative Cloud assets, Dropbox, We Share, One Drive, Google Drive, or similar.