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

public static FailureDefinitionId SpaceSeparationLinesOverlap { get; }

Public Shared ReadOnly Property SpaceSeparationLinesOverlap As FailureDefinitionId
	Get

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