He has always been a streaky player but at least he never lets his head drop and always tries.It's just what Son has always been like, for Spurs anyway. He has a run where things don't go well, and then a run where everything he hits flies into the net. I think he's due a good run soon, I don't think he has lost any of his quality yet.
The streakiness is what leaves him just short of being world class imo. Still a fabulous player and seems an amazing person as well.