Juka bows (from the Juka Lords) cannot be re-strung. The Fletchers Scissors will cut off the current string OK, but dbl-clicking the bow a) Prior to modification - with or without a string - asks for the gears to use to modify it or b) After modifying it - with or without a string - tells you it has already been modified.
This will also (probably) negate the possibility of using the special-tipped arrows on a Juka Bow - I didn't have a tub to try.