学习石亦平教授的《实例详解》遇到的问题

yollow1987

请教各位大侠，小的最近学习石亦平教授的《实例详解》，现在学习到第八章多体分析，做实例2的抓斗机的多体分析练习，按照石教授的步骤去做，但是在最后提交分析的时候，不能提交。查看.dat文件。看到如下：
***ERROR: CONNECTOR ELEMENT 3 (ASSEMBLY) HAS ITS NODES IDENTICAL TO EACH
           OTHER: 2 (ASSEMBLY) AND 2 (ASSEMBLY).
LINE IMAGE: 3, 2, 2
***NOTE: DUE TO AN INPUT ERROR THE ANALYSIS PRE-PROCESSOR HAS BEEN UNABLE TO
          INTERPRET SOME DATA.  SUBSEQUENT ERRORS MAY BE CAUSED BY THIS OMISSION
***ERROR: CONNECTOR ELEMENT 4 (ASSEMBLY) HAS ITS NODES IDENTICAL TO EACH
           OTHER: 4 (ASSEMBLY) AND 4 (ASSEMBLY).
不懂是什么意思，特此求教各位高人！