Artic fox,
More than likeliy its dirt in your V axis linear bearings, causing it to jam. I find machines that are older than 5 years that jam probably need new bearings or the bearings cleaned. The part# is TW8UUOP from nippon bearing. ON early 2424 u use to use a 100 in/oz PacSci motor that was a bit on the small size/. Keep in mind, this was before motors were made in china and dirt cheap as they are now. Motors in that day cost $200-400 each.
Manufacturer of CNC routers and Viper Servo Drives
www.LarkenCNC.com and www.Viperservo.com