This is caused by the automatic orientation of the local axes related to the global axis system in RFEM 6 and RSTAB 9. In most cases, it is sufficient to specify the member rotation using an angle or a help node. However, if the member inclination is reversed, it is necessary to split it and then adjust it by means of the member rotation.
You can find a detailed explanation of how member rotation angles work in RFEM 6 and RSTAB 9 by clicking the link below:
Member Rotation Angle Details