Problem on Nema 23 motor skipping steps

Hi,
I recently got my first ever Arduino, it is an Arduino Giga R1 Wifi, a Nema 23 stepper motor 23HS45-4204S from https://www.oyostepper.it/goods-88-M...-a-4-fili.html

and a suitable driver DM556 from
https://www.skysmotor.co.uk/goods-18...-20-50VDC.html

The driver gets power from a 48v 20a ac-dc power supply. The driver is set to 400 steps/rev. In the program seen below I'm trying to make the stepper motor do 1 full rotation (meaning 400 steps).
However, during testing I've noticed, that the stepper rotates less (each time by a different amount).
I've tried giving the motor more power from the drive (the motor is rated for 4.2a, I've tried 3.1-4.3a, 3.5-4,9 and even 4.0-5.6a), but there was no difference.

The code:
Code

#include <AccelStepper.h>

#define dir 2
#define pul 22

AccelStepper stepper1(1,pul,dir);
void setup() {
// put your setup code here, to run once:
stepper1.setMaxSpeed(1000);
stepper1.setAcceleration(200);
stepper1.moveTo(400);
}

void loop() {
// put your main code here, to run repeatedly:
stepper1.run();
}
When I start the program and images of the circuit:
https://file.io/gRoTCdUCcHDu 2
The former link leads to a site where you can download the .mp4 and .png files:

I have tried using another Nema 23 (same model) and a different driver (same model) but just got the same results. I'd we incredibly happy if someone can help me to solve the problem I have.

Its possible that the stepper is losing steps (driver issues a command, but the stepper mechanically cannot comply). So, try setting lower limits for the MaxSpeed and Acceleration and see what happens.

My guess is your sending the pulses too fast or the pulse width is too narrow. Look at the specs of your driver it will detail the waveform required

ok, i will try again, thanks for your suggestion.

Maybe these recomendations may help:
https://cnc4pc.com/faq/article/how-t...stepper-motors