Ok here some measurements on TLC driver chip:
Vcc is ok: 3.3v
BLANK is LOW
Xerr is pulsing LO-HI BUT this is also happening at the working board, at the same rate if is flashing red to indicate "CAN bus not detected". So this is not indicating a failure
Iref is 1.2v while working. Resistor measured to 3.3K, same as marking on chip
Voltage measured at outputs (OUT0-OUT15) varies from 0v to 3.2, 3.5v, pulses, etc... Mainly same on working and failing board, but like half of the LED outputs in failing board have like 0.3-0.5v less than their corresponding in the working board.

I would check the LED but I have no way to tell what model it is and whether it is driven color by color (R1-R2 / G1-G2 / B1-B2), or with a common anode and 3 cathodes, or with serial data... I can't find any marking. So I can't tell what's the supplied anode voltage

Any other suggestion for further tests will be appreciated
Thanks again