The C920 mount was loose on my C930E fixed it.
Use this rail to mount to PrusaBox.
https://www.printables.com/model/383900-prusa-box-web-cam-rail-v2
Get other parts from orig post at:
https://www.printables.com/model/161704-prusabox-enclosure-horizontal-mount-for-logitech-c
The author remixed this model.