Weapon Separates from Hands when Blending Animations per bone

Hello all!

I’m working with an asset character and the club/ spear weapon has it’s own bone.
When I did a layered blend per bone to blend the walking animation with the attack animation, the weapon detaches from the arm. It follows through - but it just looks like the weapon is a split second late after the arm moves.

Here is my setup:

Also, not sure if this makes a difference - the bone for the weapon is not attached to the arm - the weapon shows up in the arm - but the bone is separate like this:

Any ideas of how I can get them to stick together?

Thank you for any input!