If the iron is developing chips at the cutting edge in service, it suggests that it is too brittle - in other words, too hard, not tempered enough. If the iron had been overheated by grinding, that would 'over-temper' it and soften it (I think - I'm not totally sure of the metallurgical behaviour of A2 under different heat treatments). That wouldn't lead to chipping, more likely would be a more rapid dulling of the edge than usual. Apart from that, mtr1 would have noticed bluing of the cutting edge at grinding, and thought "Silly me, have to grind past that, now" - he's been working wood long enough to know that well enough.
I think the iron is too hard, not too soft.
I'm speculating now, but maybe LN had a batch of irons heat-treated in such a way that the tempering wasn't spot-on for some reason - operator carelessness, miscalibration of temperature instrumentation on the tempering furnace, whatever. LN may have sussed that, and being a reputable firm, replace any rogue irons that come to light (credit to LN for taking that approach).