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Error: Dispatcher processing has been suspended, but messages are still being processed. Occurs when

Updated: Aug 16


When posting NC code to Code Expert or generating code from the Mill-Turn sync manager, a dispatcher processing error will repeatedly pop up. The user must force quit the Code Expert application in the Task Manager to stop the errors. All Mastercam releases of Code Expert are experiencing this issue.


This error is due to a recent Windows update. For Windows 10 users, it will be either KB5026435 or KB5027215 . For Windows 11 users, it will be KB5026446 or KB5027231. This update has caused some issues with certain printers installed on a system.


This error can be fixed by changing the default printer to one built into the operating system, such as the Microsoft Print to PDF printer. To do this, go to the Windows Control Panel – Devices and Printers – Printers and Scanners page, and select the printer you wish to set as the default printer. On the printer’s settings page, select the Set as Default button.

Another solution is to install the latest drivers for the default printer set in the Windows control panel.

If you do not want to change your default printer and are not running Mill-Turn, setting the default editor in the Mastercam configuration to Cimco will allow code to be posted and edited without any errors. This is set in Mastercam by going to File – Configuration and selecting Cimco as the Editor in the Start/Exit section. Make sure to click the green check box to save these changes.

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