Lights not showing what they are supposed to

[tiagonmas]

Hi,
I have a RPI model 3b connected to this WS2812B. I have run many different tests, and none of them produce the expected results. They leds appear to light randomly, and differently every time I ran the same script. Even a simple test to light all lights as white will show random colors. It sems they have a very strange behaviour. Any ideas on what can be happening ? any help appreciated.

thanks