TIG arc flash

I'm brazing bronze art castings with a Miller syncrowave 250 and silicon bronze rod. After purchasing an auto-darkening lens, I periodically get flashed. It seems to happen when I linger over an area and get it too hot. Is it my technique or the new lens?

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There are so many helmet issues, i cant be sure ,

but if your helmet has delay setting, set it to delay longer and the sensors might have time to pick up a signal again before flashing you.

jody