My software & firmware are up to date and I have now flown around 12 batteries worth with no issues in either Phantom or NAZA modes. However, today I fired it up in GPS NAZA mode [GPS all green lights] and hovered as usual for a bit around 3m. It did not appear to hold in the usual GPS radius but started off in one direction with the sticks centred. I checked S1 and S2 position were both at top position and brought it back to the start point. It then started to fly off in another direction gaining height and speed [sticks still centred] but I managed to bring it back and land OK. After power cycling TX and Vision, everything was back to normal and it behaved perfectly for the rest of the battery. Anyone else experience this?