100.0 bounce does not maintain 100% velocity.
is the object having friction with the ground? is it affected by gravity? I’m also not sure if 100% bounce is meant to keep 100% velocity.
The block it falls on has 100% bounce on and is still losing momentum (mainly x velocity however probably because of friction)
The object density probably has something to do with it, because the object is bouncing off, but it has to push up that specific amount of mass as well. Could be wrong, someone else may know more about bounce than I do.