There is an annoying bug in the unity physics examples that I've been running into, where if you go to the sample scene "5e Kinematic Motion" and adjust the curves on the gameobject "Kinematic Body Simulated" (and I assume others as well that have curve editors) you get an error after closing the editor window and going into playmode: Code (csharp): Invalid editor window UnityEditor.CurveEditorWindow UnityEditor.EditorApplicationLayout:FinalizePlaymodeLayout () It does seem like it saves your changes, and restarting the editor gets rid of the error and allows you to enter playmode once again - but that is pretty annoying if your tweaking the curve (for instance, moving or rotating an object like in the samples and adjusting the settings with the curve) and want to enter playmode and quickly test your changes, as it will throw that error until restarting the editor. Anybody got a solution for this? The script itself is here: AnimateKinematicBodyAuthoring.cs I have updated to testing the new 0.50 Entities and unity physics, but the same thing seems to happen either way. I use unity 2020.3.31f1. EDIT: Also, it doesn't seem to happen all the time either. Sometimes it'll work properly for me now.