Dear Marcos,
As discussed in my post dated Mar 10, 2016 above, the cross-sectional 6x6 stiffness and mass matrices (including X_cm, etc.) are defined in a local coordinate along the (possibly curved) blade reference axis.
The absence of the sectional center-of-mass offsets from the NREL 5-MW turbine in Test26 is discussed briefly in my post dated Feb 23, 2016 in the following forum topic: 6x6 Stiffness Matrix of NREL5 MW Turbine.
Having a small number of stations where the cross-sectional 6x6 stiffness and mass matrices are defined (input Station_Total) should not adversely effect the BeamDyn solution, unless trapezoidal quadrature is used (Quadrature = 2) and the number of stations, including possible refinement (via input Refine), is less then the order of the shape functions of the finite element (input Order_Elem). 30 stations is not small.
Is the blade geometry you’ve defined via the key points in BeamDyn smooth? If not, BeamDyn can certainly suffer numerical problems. See my posted dated Jan 28, 2016 in the following forum topic for more information: pre-bended & sweep blade simulation with BeamDyn &aerodyn 15.
Best regards,