You have selected elements that are already part of other Systems that have assigned Equipment. The elements you selected cannot be added to this System.

public static FailureDefinitionId ElementsBelongToOtherSystem { get; }

Public Shared ReadOnly Property ElementsBelongToOtherSystem As FailureDefinitionId
	Get

public:
static property FailureDefinitionId^ ElementsBelongToOtherSystem {
	FailureDefinitionId^ get ();
}