Strage movement behavior

Hello, i trying to convert mx750 china mini lathe for cnc using linuxcnc, i connect everything, and machine alive, i can control both axis , see spindle speed etc. I tryed to see accuracy, so i clear backlash set dial indicator, and in axis app click to move 1mm, dial show exactly 1mm, then i click again 1mm in the same direction , and now dial showed only 0.99mm , i click again and now 0.98mm, seems like in every 1mm move i loose 0.01mm, when i change in axisapp to move 5mm in one movement i get 4.96mm.Always first move is evactly 1mm and every other is 0.01mm shorter. Simillar situation in Z axis.
Can all of this can be of emi noise? i connect drivers and stepper with wires without shielding. or problem with drivers or breakout board?

Are you using a linear indicator and is the indicator parallel to the axis you are measuring?