DMS revision can be added to only one active ECO (Engineering Change Order) at a time
Means DMS item can be connected to multiple Closed ECO’s (with different revision in each ECO) but only one active (not e-signed) ECO
So, if you added DMS item A to ECO AA for a specific change, and this ECO is still open, and now you opened ECO BB for the same DMS item A for another change – it cannot be done.
What you need to do is to either sign previous ECO, or remove the DMS item from ECO AA and put both changes in ECO BB