Hello, so the problem I'm having is most likely due to my inexperience with the software, hopefully a push in the right direction will get me on my way. I have created my own URDF file for a robot, the robot is close to humanoid in shape. When making the URDF file, I developed it so that the robot would be standing perfectly upright this allowed me to give coordinates in the XZ plane making them much simpler. Now, my problem is that the robot actually rests in a sort-of kneeling position so what I have done is make many of the joints revolute and made the upper and lower very close, basically fixing the joint in another position. This worked fine when creating the file n Rvis. When I bring it into Gazebo it appears as though the robot spawns in the standing upright position as the URDF was created for but then very quickly changes to the position specified by the revolute joints, which appears in turn to give some sort of momentum, throwing the robot around. Are there any simple ways to resolve this?