TPS54418: TPS54418* RIPPLE

One thing I see immediately is your input inductor. You will need an electrolytic capacitor between it and the ceramic bypass capacitors. Something with some ESR. I would try 47 uF or maybe 100 uF. If that doesn't help, please post some waveforms that demonstrate your issue.

I checked the loop response. While the BW is pretty low, there is plenty of phase margin. The design should be stable.

Hello John

adding the 470u didn't help.

See attached waveforms 

Did you ever resolve this? Perhaps you have a layout issue?