Radek
With respect mate, there sounds to be NO problem from your old pump.
That purring/ banging noise you can hear is the pump working, nothing more, nothing less. As you can appreciate as pump motors wear they tend to get a little louder, but after speaking to a long term Scorpion & now Jaguar owner (who by the way has seen the video), he has confirmed that this is an almost identical running noise to his Scorpion.
A brand new Pump-Tec pump motor with head will sound lightly quieter & smoother but over time it becomes bedded in, used & starts to wear, as it wears it becomes noisier but does not detract from its performance, especially as a well maintained Pump_tec pump should last for years
Run some acidic rinse through from the fresh water tank occasionally to help keep it scale free