I been flying the naza for a4 packs bout 40 mins now. I notice it will sometime just shoot up, or drops down somewhat rapidly while I am flying, or hovering also.
Yup, put some black electrical tape on the left side of the Naza box and see if the problem stops... The newer Naza's seem to be affected by the sunlight on that side of the sensor...
Mine has a covering that I added to the left side as well