Main breaker question 800 amp, won’t pass testing three times in a row

Ok this is a trip, Not 1 not 2 but three times this happened

800 amp Eaton breaker, a phase and c phase trip at 800 but b phase wont trip even at 1700 amps,

1 and 2 times breaker was repaired by manufacturer 3rd time bench tested and brand new out of the box,

No live power and I’ve never seen it not past testing 3 times in a row

Looking for some insight or opinions we can’t figure it out