I have the a7r, and it is working great for me, but it exhibits the light leak problem that was detailed in Feb/Mar when shooting long exposures or at ultra-high ASA.
You can see examples of the problem here:
LensRentals.com - The Sky is Falling and the Light is Leaking: the A7r Anti-Massacree
Mine produces leaks that looks functionally just like those, so clearly, it is a design flaw in the camera mount as is detailed in the article I linked to.
Anyway, I haven't heard that Sony came back with a solution to the problem. Are we on our own to fix it through the various Rube Goldberg solutions that we come up with?
I'll do a homemade solution if they haven't produced a resolution...