Highlighted room separation lines overlap. One of them may be ignored when Revit finds room boundaries. Delete one of the lines.

public static FailureDefinitionId RoomSeparationLinesOverlap { get; }

Public Shared ReadOnly Property RoomSeparationLinesOverlap As FailureDefinitionId
	Get

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