"Payload data has been discarded" error due to missing administrator rights
When using USB cameras, you may encounter the following error, especially under heavy load (multiple cameras):
Code  - Payload data has been discarded. Payload data can be discarded by the camera device if the available bandwidth is insufficient.
Solution (one of a few)
Check that you are running the application with administrative rights (right click --> Run as Administrator).
Without admin rights, the Transfer Loop Thread Priority cannot be set to real-time class (priorities 25-31). Pylon Viewer will try to set it to 25 for example.
The maximum priority available will instead be 15. This is the thread that "handles USB requests of the stream interface"
The TransferLoopThreadPriority can be checked in pylon viewer under "Stream Parameters". It is also accessible via the pylon api.