i think you have a broken 'X' axis cable. the x cables routed under the saddle and thru a drag chain under the column. this drag chain has a bend in it which opens and closes as the 'y' axis moves backwards and forwards. this flexing causes the cables to fail. if it is a broken power cable then start the machine and if you can re-create the problem by moving the 'y' axis backwards and forwards BEFORE you align the machine you could then remove the 'x' axis motor cable from the bottom of the drive and try moving the 'y' axis backwards and forwards and the fault should not occur. a broken feedback cable is more difficult to diagnose. if you go to the back of the machine and look in the area of the 'y' axis motor you will see the cables coming from the drag chain under the column. is one of the cables an orange color? or are they all grey- sorry gray. the original cables were gray and these become brittle and break with time. they were replaced with an orange coloured cable which is much more flexible and not prone for failing. i use a test cable which i run round the outside of the machine to prove out cables. broken power cables are a common enough occurance and probably the worst job to do on these machines.
best of luck