The ten LEDs on the board, used for debugging (SML-311UTT86K) is not available anymore.

The SML-311UTT86 would be the same LED but they have a difference in brightness:

with K: 4.0 – 6.3 mcd at 2mA
without K: 0.9 – 2.5 mcd at 2mA

Suggest to replace
SML-311UTT86K by
SML-311UTT86

Problem and solution from Janz. Agreed with Erik.
LED type will be different on productions from August 2017 on.