Had got the same problem.
I do own a Wren2 and a Phoenix. The Wren2 is quite perfect (for me).
After some time with the Wren I thought of an upgrade and ordered the Phoenix.
When receiving my Phoenix I was totally disappointed. I can move the bellow in and out as if I had pressed the "air botton".
When playing tunes I always go out of air.
After some discussion with the support, I have sent it back to Ireland.
A few weeks later, it made its way back to me. "All ok" with your Phoenix was the result.
It still feels leaky. I am not able to play a slow air on it withput getting a lack of air.
My Wren2 is holding the air much better than the Phoenix ever will.