必须使用更新计算点方式才行

src/Editor/SnapDragServices.ts

@@ -111,9 +111,7 @@ export class SnapDragServices
                 }
             }
         })
-        if (pt.Status == PromptStatus.OK)
-            this.lastSnapPoint.copy(lastP);
-
+        this.UpdateLastPoint();
         this.UpdatePreLine();
         app.m_Database.hm.EndCmd();
         app.m_Editor.ClearSnapEntity();