Wobbling movement on Y-axis

V-Core 500 - when the toolhead is moving on the X-axis, there's a slight wobbling movement on the Y-axis: https://photos.app.goo.gl/upjR6oKfTTsr9JJs7
(Tape placed to show the movement)

After checking all pulleys and motor shafts (all seems fine) I suspect bad belts - they jump up and down: https://photos.app.goo.gl/8ENQ5pjKQ4DvG5rb6

Can someone give me a hint?

Google Photos