Mine has done the same thing now on both sides. 2015 as wellThe right hand DRL has partially failed on my 2015 treg.
Center part is working, the bottom edge is not.
Rang a dealer today and was told the LED not a replaceable item, so fix is a complete headlight $1400.
Seems odd that the LED has failed inside 4 years but insane that the 'fix' is complete assembly replacement.