All motors are notching

Hi!
Can someone help me?
I have assembled my new reprap prusa i3 and everything seems to work well, except from the motors. On first connection of the board,
the motors run smooth the first 3 seconds. After that motors start to notch with a high noise.

When we jog it 100mm, the length can be between 50 and 80 mm if the motor is notching and exactly 100mm the first seconds when it move smooth.

Have someone seen this issue before and have an answer?

See attached video:
my reprap

I found out that my step drivers were extremely hot in just a second after I start using the motors.

Have any of you experienced the same?

Your drivers are overheating, they go into thermal shutdown briefly, which causes the knocking sound.

You'll need to turn down the current limit, and/or apply some cooling like a fan blowing across the board.

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Thank you very much. The Vref on the pololu stepper driver was 0.83V; - current about 2.2 Amp. Reduced the Vref to around 0.4V and problem solved!

If someone read this post, you will find more information about this issue here:
Calibration
Pololu_stepper_driver_board

As far as I can see, the current for the motors cannot be set in firmware.

Some boards use digipots and you can set it in firmware. But not anything that uses a Pololu stepper board.