Simpack - Bogie frame displaces while running

Guyz question: I am designing a bogie using Simpack simulia. When performed the preload and Static eqbm offline I didn`t receive any fatal errors, just a warning that vref is too small. Everything is fine without anz errors or fatal errors apart from small vref warnings. After that when I ran the simulation the bogie frame displaces, axle box vibrates and runs with the wheelset. you could see 2 videos here. One with 2 primary susp and the other video with 1 prim. susp. The video with one Prim. suspension is the problem here. The bogie model with one primarz suspension is developed from the perfectly working bogie with 2 primarz suspension. But for the newly modified bogie with single prim. susp. the bogie frame displaces while running. 

Given I am a beginner with this software, I need some inputs or suggestions from your side to resolve these issues. thanks!