I have not been able to find much information on problems with the MD12.
Here is one link that discusses a problem:
The MD12 is discussed near the bottom of the page.
I was referred to this link thru CNet. I have had the FE for a while and recently purchased the MD 12. I have noticed that when it is attached and the shutter speed is set at Auto, it jams. When using ANY of the other speed selections, it works perfectly. Am just wondering if this is a flaw or a normal condition with the MD and FE. thanks for your advice.