Hello,
I'm in the process of building a core xy machine with dual Z bed. I'm using duet 2 wifi board. One of the motors turning half the steps as the other. If one is turning 2 the other is one. I have one of the motors connected to E1 the other to Z output.
I have swapped the connectors (Z to E1, E1 to Z) and that particular motor is still turning half. They have detachable cable, I have swapped their cable to make sure it is not a wining issue, still same motor turning half the steps.
Is the stepper toast?

Sounds like you have one 1.8 degree stepper motor and one 0.9 degree stepper motor

they are the same. made a video [GDRIVE LINK]