The correct fix is not just to separate the wires, but also provide each with a ground return wire next to it.
If you use ribbon cable to send signals a good approach is make every 2nd or every 3rd wire ground, so
that every signal is next to a ground return. This greatly reduces the magnetic pickup to the wire from
stray fields from high current circuitry.
With CAT5 cable each signal nees to be individually paired with ground in a separate twisted pair. You can
use Vcc instead of ground as a return if you wish.