It could stall right there for 3-4 hours sometimes.
If it is NOT going to be done in time and you have figured your time-temp calculations correctly, foil it with moisture in the foil and crank the heat.
I do my entire cook at 375 and I get the BEST most MOIST Brisket every time!
Put it in an aluminum pan and add a Beer. Then cover the pan with foil. Then you also have all of those wonderful juices, too.
That's just how I do them.