12V 19A LT8390 CCT output keep going into hiccup mode when a load is applied.

Hi All,

My circuit use a LT8390 to  convert 24V 10A supply to 12V 19A(max).  It suffers from the following issue:

1.  If a load > 0.5A is add the output goes into oscillation 12V to 11.2 

2.  PGOOD output seems to reset and power in a the sequence described in the data sheet as the "Hiccup Mode"

PDF

Please does anyone have any suggest as to why my circuit goes into this Hiccup mode as soon as a load is applied

Thanks

Enyi