Well... surprises do happen!
Went to the range this morning to try the deflectors again, and here are my results. I set both deflectors farther forward than before. This time, I lined up the solid part of each deflector with the opening in the receiver so that none of the slots were in the ejection path.
Do the new deflectors have a different layout than the original? The original has slots all the way to the end and maybe 1/4" of solid material between the last slot and the edge.