Point of sale terminal battery on AS 17 catches fire
Aircraft would have most likely been over max landing weight and that in itself requires an overweight landing inspection. Top it off that a fire extinguisher was used and don't believe there is MEL relief to allow the airplane to continue without it.
Just a guess but also on the rescue flight inbound is AS personnel (crew, mechanics, and possibly CSA/management). Crew is probably deadhead but are still on-duty in the eyes of the FAA and so they probably still have duty time to fly but only make it to GEG where another crew can be ferried in easily to finish the flight. Mechanics will probably replace extinguisher, do some general checks that are just enough to maintenance ferry.