WS2812b decoupling capacitors

Before connecting the WS2812 to a power source, connect a big capacitor from power to ground. A cap between 100µF and 1000µF should be good.

Just like the WS2812 breakout boards, we recommend adding a 0.1 μF capacitor between each WS2812 LED's VDD and GND.

https://learn.sparkfun.com/tutorials/ws2812-breakout-hookup-guide