Hi Brian, could you please post the .3dm file of your object as well? That would help to see what might be going wrong in your particular case.

It looks like you may have some pretty tight bends in there, one thing to look out for is that it does not work well to ask for a fillet radius that is larger than the radius of the tightest curve in the edge to be filleted.

There is some description and illustration of that one in the fillet documentation:
http://moi3d.com/1.0/docs/moi_command_reference7.htm#fillet

- Michael