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


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.

Dispatcher Processing Error


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 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 try installing the latest drivers for the default printer that is 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.

CIMCO Editor Select

If you are running Mill-Turn, you are required to use Code Expert as the NC editor. In this case, before selecting the G1 button in Code Expert, click File – New – Code Document. Once you have created a blank Code Document, you can now go back to your sync manager tab and click G1. The error appears to only occur when a NC Document is the first type of file opened during a Code Expert session. If you leave Code Expert open, you do not need to perform the new Code Document workaround again for future posts. You will only need to repeat this process when a new session of Code Expert is launched.

New Code Document

Technical Support

Get help from our team by Calling us at 800-364-1652 x 3. You can also get assistance by clicking the Technical Support button or the Email Our Experts button below. 

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