I recorded a detailed video showing how Unity 2018.2 affected my project, comparing the same features both in 2018.1b11 (where everything works) and 2018.2.1f1 (broken physics). Tested with 2018.2.2 and .3 later, same problem. What's happening? Kinematic rigidbodies should NOT be affected by the forces, I learned... It's impossible upgrading my project to all newer Unity versions. It worked in almost the same way with Unity 4, 5.x, 2017.x up to 2018.1b11. But final releases of 2018.x broke everything. I tried many changes, including leaving all child kinematic rigidbodies with the same interpolation settings... Nothing seems to work. Tried also Physics.autoSyncTransforms both to true and false, same bugs... Is that a bug or something was changed?! It's hard to believe that this critical bug still exists in a "final" release, if it is a bug... 1 - Moving kinematic rigidbodies inside a moving non-kinematic rigidbody have a strange behaviour, they are left behind. Watch people in my bus, shown at 8:35. 2 - Each time we put the vehicle on the ground from some height, the child kinematic rigidbodies are moved a little bit to the top on y (check at 6:19 to 7~8min). Unlike the people on a local waypoint system inside the bus, buttons don't have any script moving them, they have a collider and a rigidbody just to recognize mouse clicks. Both problems don't happen with Unity 2018.1 beta 11. Tested with 2018.2.3, bug still exists besides some fixes in physics. This bug seems related to this one, I'm not sure: https://issuetracker.unity3d.com/is...ild-object-to-be-misplaced-after-the-movement My project is too big/too complex to send a sample project, I may try exporting only a bus and some part of the map to the bug report, but I cannot do it right now.