Recently, we proposed a dynamic reaction path (DRP) analysis with vibration mapping and examined symmetry-conserved processes in the reaction SiH4 + H- --> SiH5- (side and front attack). A key feature of this study was an analysis of the Berry pseudorotation mechanism in SiH5- from the viewpoint of vibration-vibration interactions. In the present study, we extend this methodology to deal with symmetry-relaxed attack by using a function that estimates the distance between any geometry and a reference geometry in configuration space, in order to examine the relation between the incident path of H- and the pseudorotation. When approaching SiH4 from the side or back, the H- changes its path toward front attack, due to-the high energy requirements for the side and back attack paths, resulting in a vibrationally active SiH5- with accompanying Berry pseudorotation. On the other hand, in a frontal or nearly frontal attack, SiH5- seems stable with no pseudorotation.