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LT3716 - IC burnt at pins ISP ISN

Hi 
we have several boards that return from customers, were pins 2,3 are damaged    (less than 1% of boards) 

any suggestion what is the root cause  ?

there are 2 Chip on board each contains 16 LED with ~25V fall with 2A current

the board is working  with up to 1mSec pulse up to 60Hz pulses/Sec  

Those pins are up to 80V and never go above 57V at our design 
Regards