Adjacent slope-defining lines must have identical eave heights; the highlighted lines do not. You can use the Align Eaves tool to have the eaves aligned for you.
Namespace: Autodesk.Revit.DB
Assembly: RevitAPI (in RevitAPI.dll) Version: 26.2.0.0 (26.2.0.0)
Syntax
C#
public static FailureDefinitionId DifferentOffsets { get; }