How big is the brisket? What temp are you cooking at?
Most briskets will seem to gain temp fast at first but then they will slow down and usually hit a stall where they can sit at one temp for hours before climbing again.
Ride it out!
I see this is your first post here so when you get a minute would you swing by "Roll Call" and introduce yourself so we can give you a proper SMF Welcome, Thanks!
A small 5 lber probably won't stall much or very long but will slow down as the temp gets higher. Your chamber temps are good so I would leave it alone and let it smoke.
If it gets done too early you can wrap it in foil then some towels and hold it in a cooler, it will stay hot for hours.
There's also nothing wrong with smoking "hot and fast". I've been experimenting with that myself and the results have been pretty decent. The beauty of smoking meat is that even the mistakes are pretty delicious.