Hi Avila, the problem is there isn't room to fit a fillet with radius 3 because of the previous fillets.

Observe this area of the model as the fillet grows from radius 2 to 2.5 to 2.9:



Radius 2:


Radius 2.5:


Radius 2:9:


Notice how the side indicated above is getting smaller and smaller? At radius = 3 it will be collapsing in on itself.

So to apply a fillet of radius 3 there, you would need to do it at the same time as the other pieces that also had radius 3, that will allow the filleter to make a corner juncture patch in that spot instead of trying to build a fillet along the other previous fillet's edge.

On areas where fillets will collide into each other it's best to put all fillets of the same radius at the same time and in general put largest fillets on first and smaller ones after.

So because of the previous fillet geometry that the new fillet will need to cross over you will need to use a radius of less than 3 there so it can fit around the tight corners that are now there from the previous fillet.

Hope that makes sense.

- Michael