i´m soo sick of find problems with Unity Animator specilly with mecanim and animator´s maks, and i know i am NOT the only one! If you just try to make a animator controller with diferent layers to make a Aim animations merging staes on bottom and upper parts of a body, you knoew what i mean.. if not, sure, sit and take a coffe, i will explain: when we have this set of layers on animator (you can see an exemple bellow), the impossibility of partial sync between animations can give, us a problem, or a lot of problems with rotation errors on character. the state FreeLocomotion is THE SAME STATE on both of layers, CTRL-C/CTRL-V, but trsnlations to the diferent states that don´t exsists on Base Layer, i belive the unsynked time between they causes the rotation errors i mean. (Bellow a little exemple using a navMesh Agent with those layer set, i forget it to show but the states when he get the phone is on second Layer, i´ts not a hight one but it´s all i can show for you guys) https://imgur.com/a/m5AK5QJ With this, think on a strafe move blendtree Coppied to both of layers, wit all the states attatched to him on BOTH OF LAYERS IDENTICAL, but, the upperBody layer has transitions to ... get a weapon or... take a phone as the exemple, ... there it is! on some cases, i see my character wit a soo wrong rotation that looks like he was with broken legs or something... Why i don´t try to use Synk options on animator? because as i say it, this nulls the diferent states that we need on this cases, using jut the base states. Why i don´t use maks on Base layer too? belive it, i try EVERY POSSIBLE COMBINATIONS onf layers with diferent maks, but this junt turns more visible the unsynked time and mantains the erros because every unsynked loop exagerate a littlebit more this roations. Why i simply don´t use Humanoid? i need IKs for some cases, and as i say up there diferent combinations of maks don´t work, soo... you realy think i can try this and put on the risk to make a custom IK for Generic jut because of this? if Yes: Men we have the Animation Rigging package now, come on, use it! I try it, and as my second layer use´s override mode, so, the riggng auto-forces to zero ALL THE WEGHTS, making it useless for my cases.