Prompted with the error from previewing an invoice in open orders:
Internal thread prevents Print Dialog to be shown. External component has thrown an exception.
This is caused when the preview is shown inside a print job. This is not an error as the printer settings cannot be accessed while in preview from the Open Orders screen
There is no solution for this as this is not a bug rather a warning that the settings cannot be accessed.
If you need to select a printer do so when it prompts before the preview is opened.