The Part is inside a Model. It’s anchored. No velocity. No RotVelocity. So why does the Humanoid bounce up and down on it?
Here’s the raw XML of the model and the part it contains:
<roblox xmlns:xmime="http://www.w3.org/2005/05/xmlmime" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="http://www.roblox.com/roblox.xsd" version="4">
<External>null</External>
<External>nil</External>
<Item class="Model" referent="RBX81BB895BF7B94417B1C1DE1DDFFEC9A2">
<Properties>
<CoordinateFrame name="ModelInPrimary">
<X>0</X>
<Y>0</Y>
<Z>0</Z>
<R00>1</R00>
<R01>0</R01>
<R02>0</R02>
<R10>0</R10>
<R11>1</R11>
<R12>0</R12>
<R20>0</R20>
<R21>0</R21>
<R22>1</R22>
</CoordinateFrame>
<string name="Name">MapModel</string>
<Ref name="PrimaryPart">null</Ref>
</Properties>
<Item class="Part" referent="RBX0A2D361788974B3C95D8A65421EA49C8">
<Properties>
<bool name="Anchored">true</bool>
<float name="BackParamA">-0.5</float>
<float name="BackParamB">0.5</float>
<token name="BackSurface">0</token>
<token name="BackSurfaceInput">0</token>
<float name="BottomParamA">-0.5</float>
<float name="BottomParamB">0.5</float>
<token name="BottomSurface">4</token>
<token name="BottomSurfaceInput">0</token>
<int name="BrickColor">194</int>
<CoordinateFrame name="CFrame">
<X>131</X>
<Y>-4.5</Y>
<Z>29</Z>
<R00>1</R00>
<R01>0</R01>
<R02>0</R02>
<R10>0</R10>
<R11>1</R11>
<R12>0</R12>
<R20>0</R20>
<R21>0</R21>
<R22>1</R22>
</CoordinateFrame>
<bool name="CanCollide">true</bool>
<float name="Elasticity">0.5</float>
<float name="Friction">0.300000012</float>
<float name="FrontParamA">-0.5</float>
<float name="FrontParamB">0.5</float>
<token name="FrontSurface">0</token>
<token name="FrontSurfaceInput">0</token>
<float name="LeftParamA">-0.5</float>
<float name="LeftParamB">0.5</float>
<token name="LeftSurface">0</token>
<token name="LeftSurfaceInput">0</token>
<bool name="Locked">false</bool>
<token name="Material">256</token>
<string name="Name">Part</string>
<float name="Reflectance">0</float>
<float name="RightParamA">-0.5</float>
<float name="RightParamB">0.5</float>
<token name="RightSurface">0</token>
<token name="RightSurfaceInput">0</token>
<Vector3 name="RotVelocity">
<X>0</X>
<Y>0</Y>
<Z>0</Z>
</Vector3>
<float name="TopParamA">-0.5</float>
<float name="TopParamB">0.5</float>
<token name="TopSurface">3</token>
<token name="TopSurfaceInput">0</token>
<float name="Transparency">0</float>
<Vector3 name="Velocity">
<X>0</X>
<Y>0</Y>
<Z>0</Z>
</Vector3>
<token name="formFactorRaw">0</token>
<token name="shape">1</token>
<Vector3 name="size">
<X>28</X>
<Y>3</Y>
<Z>6</Z>
</Vector3>
</Properties>
</Item>
</Item>
</roblox>