we have the tps54550 in a new design - of 4 boards all were initially operational but one is now failing with a very fast soft start and overcurrent "hiccup" oscillations. the ss/ena pin is open I this design. the load aside - I am measuring a simple dc resistance to ground on the PH pin of 15 ohm for a failed unit - with other boards at 1k, and a suspect one at 35 ohm. question - is there a failure mode/indicator of the 54550 that would cause the PH pin dc resistance to ground to reduce as described please.