Here’s why your machine is doing this.
The standard LR3 leadscrew is T8 4 start 2mm pitch, 8mm/Rev.
The alternate ones that Ryan sells are 2 start 4mm pitch.
Your lead screw is 1 start. You will need to adjust the steps/mm for your Z axis to account for this difference. I bet you find that your axis moves exactly 1/4 of the commanded distance, so you’ll need to increase your steps/mm by 4x the current value.
The impact will be that your Z axis won’t be able to move as fast as with a 4-start, but this may not matter to you. One nice benefit is that your Z axis will likely not drop when the steppers are not powered.