This advice is incorrect. While it will technically work, it is not the right way to do this. By disabling physics on ALL of that characters bones, their hair, clothes, skirts, and other accessories will not have real-time physics.
This thing usually occurs because a bone collider is present in the scene. You have to select the bonecollider, then open KKPE and look at the bones it is effecting. KK studio is weird and for whatever reason, bone colliders will influence tons of bones they are not configured for on scene loading, or when swapping characters, changing outfits, adding new characters, etc.
It will have a lot of bones its effecting, but you will usually see one specific object like a penis or something with just a few bones selected. Deselect all, then manually reselect those specific bones and the scene will be restored to its original state, with working physics for all other elements.