I posted this a couple days ago but didn't get any responses. I'm hoping it's because I didn't have a file that was able to reproduce the problem. Now I do: If you open this assembly and try to rotate the "trigger" block, it should rotate the "gear" with it. Instead the gear just shoots out of place. Alternately, you can rotate the bracket block, which strangely changes the "ground" in the scene. Undoing this then results in the same displacement of the gear part. I have no idea why this is happening and I have no idea how to fix it. Any advice? I'm also getting some very strange and unpredictable mate conflicts in this assembly, which I'm suspicious is related. At this point my thought is to just give up on layout sketches altogether. They're either buggy or I don't have enough Solidworks experience to make them useful.