So, I've had a couple of Leaf digital backs and love them. I recently ran into a problem where EXIF was no longer being stored in images recorded to a CF card on my Leaf Aptus-II 5 (same as an Aptus-II 22 I think). If I shot tethered, I got full EXIF. After a lot of frustration and 2 weeks in the shop, the local tech was told by Mamiya that you cannot put any 'strange' characters in the copyright field. Low and behold, I had put a copyright symbol in there. Deleting it restored the back to full working order.
I ran a month without EXIF and vaguely wonder what the heck lens I used in a few shots from that time. I thought I'd post this solution here just in case anyone else runs into the problem. Google didn't wind up helping out at all.