Doing a motion analysis in Simulation Standard - using a model with a vertically opening door and springs to assist opening (not enough force to open), and modeled with mates that limit the distance (using gas springs which have a stroke length), if the door material is set to steel, the motion study is correct - the door does not move. But when the material is set to Pine, the door immediately goes full stroke, then past, then the door disappears sometimes. Occasionally, some phantom mate errors will show up in the model and/or the motion analysis, sometimes in a sub-assembly, which has no bearing on the motion, so there is some instability in my SW installation (another discussion). BTW - the spring forces are NOT enough to open the pine door, but if they did, the door should stop at the limit distance mate. I was reducing the weight of the door (with a cut in that part) to see when it would open. It constantly exceeds the limit distance mate - how do I control this?