It is wild! Before I herniated my diaphragm five years ago I was not able to come back up in Karandavasana but now that my surgery has healed I am! It is amazing! A friend of mine thinks that the diaphragmatic hernia was congenital. That would explain why I couldn't come up before but I can now. I needed the strength of the diaphragm in order to accomplish the pose.
I still cannot come down though without first my hands coming together when I go into Padmasana and having to put the crown of my head onto the floor. When I do come down I am sliding my face along the mat and slowly bringing my knees onto my elbows. It is not correct but is better than what I had been doing.
Lately I haven't been holding it for five breaths but coming right back up. But what is encouraging is that when I do come back up I am able to lift my head and face up off the mat and when I get all the way up jump back into Chaturanga.
I think today I will try and hold the posture for five breaths before I come up. I think this will help build strength in my shoulders. That is where the weakness is now. In order to build up the strength I am really muscling into Chaturanga in all the vinyasanas.
Here is a video of Sharath doing it correctly. I have a lot to work on!