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Hello, I am trying to do a linear buckling analysis on a telescopic mast of 12m. The assembly has a blend of 1D, 2D & 3D elements followed by contacts. Anyways i have taken care of all the parameters like element quality, free edges, T connections etc. As usual, I carried out a FREE-FREE Analysis first followed by MODAL & then a STATIC Analysis (Gravity Loading). All the rigid body modes have been eliminated and my modal frequency are as follows 0.676, 0.677, 6.75, 6.78, 19.53, 19.70, 39.55, 39.71, 45.30, 59.39. I don't know why the modal frequency fetched such initial low values and how to interpret the intermediate frequencies occurring in pairs? The Static Analysis results are also satisfactory with a max displacement of 0.235 mm (Mag) and stress of 11.34 MPa.The stress flow pattern is also satisfactory. Now when I simulate a linear buckling analysis I get this error: ERROR 165- Gram-Schmidt reorthogonalization did not converge. This is caused by ill-conditioning of the shifted matrix in Lanczos run. I have gone through a few other posts in this forum which said to remove rigid body modes, but i don't have any rigid body modes as such. And it is quite evident from the static analysis that my model is well connected and contacts are acting. Could you please let me know how to resolve this issue? Thank you.