Why does my task name show up as the task's internal task ID number when I save the project back from MSP to PPM?
If a task is added in MSP without a name, and saved back to PPM, PPM will change the name to the internal task ID, as task name is required in PPM. You will also see this if you add a blank task row in your MSP project with any tasks underneath it. A blank row is considered a real task but with no name.
It is best practice to create all tasks with names in MSP since task name is a required field in PPM, and a blank task name can cause unexpected issues such as names being changed to internal IDs when saving the project back to PPM.