Is it still on the rise then?
The shrinking is not limited to Aeros.
I find this very odd. I have had dozens of jackets, in goat, horsehide, cow, steer, kangaroo and capeskin and I have never had a jacket stretch or shrink even by a millimetre. And I live in an extreme climate of unbearable heat and humidity along with cold and rain. I have even put many jackets through the washing machine (with detergent) to break them in. No change in size. What can be the cause here?
Unless you measured, how would you know? I would expect that one might notice shrinking sleeve length, but a little extra or less length in the body isn't likely to be noticed unless you measured (and actually remembered the original length).
did you measure it this exact same way before? One mistake I made measuring mine once, I did not have the top of the tape measure hooked on top of the collar seem, I measured it from just below the collar seem. If you're convinced you are measuring it the exact same way as before, I'd contact aero. If it really did shrink .5", sounds like a faulty batch of leather
btw I don't know how you could arrive at an accurate back measurement, measuring it lying flat like that. You need to hang it