One of the problems that I've seen with machining inside corners is that the machinists typically grab a cutter that will fit and that the one designing the part tends to put in fillets that are nominal size. When doing this, the cutter goes squarely (90degrees) into the corner and cutters don't really like that. What I started doing a few years back was to bump my fillet sizes bigger than nominal, like .280" instead of .250". What this does is allow the CAM program to make a radius in the corner which has a slight decelerate/accelerate moment making the cutter much happier. Before CNC's, the machinists had mainly the nominal sizes and with CNC's it is a moot point now as the lazy machinist doesn't have to do the math.
I hope this gets to the point of what you was asking, if not, thanks for reading!