I got a problem in doing difference operation, and it turned out to quit in file mesh.isct.tpp, line 1064, where para nTrys decreased to 0. And I find if I increase nTrys to 10(5 previously), it will be fine. Usually it takes 5-7 times of loop to perturbing positions. So, can you increase nTrys to 10 or more? Or is there any other solution for this problem? Maybe something wrong with the mesh?