I see some out-of-round bokeh in the upper left of the image made at F/2.8. Was this image cropped from the original 35mm negative? If so, was this corner of the image near the edge of the film frame?
Looks like something funny is happening in that corner of the image, like the bokeh has a ghosty halo on the bottom half.
However, I don't think I can help you with a sample shot.
Is your Xenon the type where the outer lens element unscrews? Perhaps it's not threaded tightly back in place, or maybe there's some debris on one of the optical elements?
~Joe