I've also tried to buffer the signal,
TLC's are made for daisy chaining so you would expect that there are ways to link a great many
The library uses pin 13 for the clock signal,
can it be that the led and resistor on this pin have an influence,
However how farther down the chain i measure how larger the amplitude becomes (which i think is strange).
with 6, 5 will work, but with 12, 8 or 9 will work.