Alarm 104 means that the axis is not moving as fast as the controller is expecting it to move.
I think a 1998 machine has brush type servos. You may need new brushes or all the dust inside the motors may need to be blown out.
What does the servo load show when you do Y axis zero return? If it goes high but the motor is not running fast the problem may be carbon dust shorting inside the motor. If it does not go high or fluctuates then I would suspect worn brushes making poor contact.
An open mind is a virtue...so long as all the common sense has not leaked out.