Hi Brian, over here the top edges fillet fine up to a radius of 0.9 or so:



Any much more than that and there isn't room for the fillet to fit - you can see above that at radius 0.9 the side wall surface is trimmed down to a small thin piece.

From your bottom fillet it looks like you were trying a fillet radius of 1?

Since your entire object is only 2 units tall, that would cause the side parts to be completely eaten away - that will cause the fillets to fail. You have to use a smaller radius on shapes like that.

- Michael