Appears Im having the same issue as this thread reports:

http://www.phantompilots.com/thr ... imits.100578/page-4

In my app, my RTH altitude is set to 50M.

Did a basic flight at the usual field I fly at, at an altitude of about 150-160 feet altitude. About 3:45 mins and about 1367 feet distance into the flight i initiated RTH. Altitude at that point was 160 feet. Unbenknowst to me (until after the flight/after I reviewed the logs) She then stopped all horizontal movement and automatically rose up to an altitude of 524 feet.  At that point, the vertical climb stopped, and it proceeded it's horizontal flight back to the home point. At that point, it automatically increased altitude to 610 feet and climbing before I noticed what it was doing.  (thank goodness I had plenty of battery life) I then interrupted the RTH process and manually reduced altitude and landed safely.

Confirmed 100% of all of this looking at the flight record section of the phone app.

Received this Mavic two weeks ago, have had no popups on the phone app (GO 4) to perform any form of update.  

Anyone else here experience this?

DJI Support: Your thoughts/input?  

wow,   what mode where you flying in,   and what did you have rth set to?  really strange,  

I was in GPS mode, and had RTH set to 50 meters.  

Very concerning to have the craft automatically rise up on it's own well past 400 feet altitude (Im in USA) and was continuing to climb until I intervened.

DJI Ken: I'd like to upload the flight data from that flight and have it analyzed. Can you assist?

I reported what appears to be the same issue back in early December: http://forum.dji.com/thread-75543-1-1.html