Apologies if these are total newbie question, this is my first big boy drone. Have flown my YTH on three occasions now. On day 1 the LED indicator went solid purple, which I believe means it has GPS and is locked. If I enabled RTH it landed within a metre of where it took off. Day 2 and 3 the LED indicator would flash purple rapidly, then a brief white and repeat. The controlled said GPS acquired with 11 satellites on both days. In flying it would hold position happily, however enable RTH and it would fly roughly back to me but would land anywhere up to 40m away. Is this a sign that I need to do a compass calibration? Or something else? Also if I do a pan using the gimbal it stutters, it won't do a smooth turn. Is this to be expected?