X-Pro2 with Nikon Ais Lenses

I'm using a Metabones N/F - X mount T adaptor with a Nikon 50mm/1.4 Ais. I've got the camera set to "shoot without a lens." I can manually control the shutter but not aperture. Changing the stops on the lens has no effect. However, it works fine when using the Nikon 24mm/2.8 Ais. Any suggestions? Thanks.

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