Custom rig collision problems

hello everyone im trying to make a custom character with meshes, and it seems the collisions are in the shape of the original pose as you can see in the video below
robloxapp-20240627-1632136.wmv (1.8 MB)
and im wondering if i have skill issues with myself or its just the engine

Are you using MeshParts, or normal Meshes?

i think its meshparts becouse there is more parts binded by weightpaint and a rig