Dear community, I posted this thread in Mathworks Simscape Community two days ago or so. And I have decided to record a video and post all the information in this forum. This is my first time, so hello and thanks for reading! Last month I was playing around with Simscape Multibody and I realised something. They have a "four bar linkage" preset to simulate its physical behaviour, so I changed a bit the initial positions and I found this: I have simulated the same mechanism in Autodesk Inventor and It behaves as I expected (as a pendulum). I supposed that the simmetric position in this case should be the equilibrium position, the attractor. Then, I decided to create a new simulation in Matlab and this very weird situation popped up. But I do not see why, how, where... I mean, It goes far beyond my understanding. Some data are: -Connector Link (Yellow bar): -Density: 1000 kg/m^3 -Volume: 10x2x0.5 cm^3 -Rocker Link (Red bar): -Density: 100 kg/m^3 -Volume: 25x2x0.5 cm^3 -Crank Link (Blue bar): -Density: 100 kg/m^3 -Volume: 25x2x0.5 cm^3 Conditions: -No friction. -No external foces. -Just gravitation acting. -State targets (initial positions): specified in the video. Sorry about the size. Please watch full screen in 1080. I would appreciate your comments on this issue, please, I really need it... Thanks again!