Cannot add assignment while change assignment is pending approvals

Summary:

We are unable to add assignment for an employee while change assignment is pending approvals

Content (required):

A transaction for Change Assignment was initiated for an employee and is now pending approvals. In the meantime, the HR user wants to initiate an Add Asignment transaction for this employee but is receiving the following message: Approvals are in progress. Info is locked.

Do you know why that is? This is a new assignment they want to add, not related to the assignment with the pending change.

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