It may be caused by damage at the hole of the filling nozzle. You may fix the hole by taking out the filling nozzle. Grind the surface of it gently with water finish sand paper after fixing the aperture of the nozzle. Or the sealing ring of the filling head is damaged, just replace the sealing ring.

Jam blocked in the filling channels, mainly at the tank inlet or in the filling nozzle, just check and clean it.

At the time of filling large size and insufficient tank feeding which may cause instability of liquid level, please increase the feeding quantity or turn down the ball valve above the filling head, reset the filling time (add more filling time ) to slow down the filling.