We get a number of project managers using MSP get the "Summary Task Assignments Not Supported" error when they download their plan and make no changes.
This implies that the resource assignment against the summary task is already in the system.
When investigating we have been unable to either assign a resource to an existing summary task or to change a task with a resource already assigned to a summary task. Which begs the question, how did they make their way in to the system?
Has anyone experienced this? Any ideas on how the original assignments are caused?