I am working on a 4x4x6 Led cube powered by an Arduino Leonardo. The rows are multiplexed using a Johnson counter and a ULN2003 Darlington transistor setup. When I program reset the Johnson counter so that only one layer is grounded and power on the LEDs one by one, two or more LEDs in the same column will light up This depends on which layer is grounded. Then, after a certain number of LEDs have been switched on, only the LEDs in the grounded layer light up. (This number also varies with the layer). I have checked my wiring and do not think it is a short. I am at a loss as to the cause of this problem and rely need some help.