WS2811 12v

I come to you today because I have a problem with my WS2811 strip, the 5v work well but not the 12v, they sparkle. While inquiring I read that a level shifter was needed. What I bought and put but it still doesn’t work. I use a WS2811 12v led strip, a nodemcu, and the level shifter link below. Is it possible to get some help please ?

Those level converters look suspiciously like I2C designed devices that are often too slow for WLED.

Can you post some more details about your wiring setup, number of LEDs, MCU type, etc. etc?
Do you have common grounds between your 5V, 12V and data lines?

What happens if you try and drive a small number of 12V LEDs (say 20) and/or set the brightness low?