Was the cable working okay not so long ago?
1] Using the correct cable? replace with correct item
2] Is the cable old and stretched bent or damaged? replace with new item
3] Is cable correctly routed? reinstall correctly
4] is actuator arm correctly installed? reinstall arm in correct position.
All the above work, try those before playing with the angle grinder and scaring a finger.
yes you can shorten an outer but if the cable isn't routed correctly and you do shorten it then it will be out of adjustment when the cable moves during your next ride. if you need to remove outer then its not the right cable or you have changed something else like the routing or the position of the actuator arm.
