First of all, the manual says RTH will work when it goes way pass the 20m mark.
I had a panic attack when i was flying my spark doing the quickshot(circle) and didn't notice the radius was too big that it flew pass a building behind me. Seconds after, I lost the sight of the drone, my dji go app went blank(disconnected). That's when the panic attack kicked in...lol.
I was just hoping that it didn't fly away. I immediately ran out to the open space hoping to get the signal back but since it was too high up, it failed to reconnect. Then I saw it went up to a certain altitude and flying back to the take off point. By then, I'm pretty sure that the RTH was activated...It worked flawlessly. Pheww... The app got reconnected when it reached about 10m or so and I took over the automated landing and land safely. Oh ya, forgot to mention that I was controlling the AC using just my Iphone that day.