Rhydm:
That worsened the situation
When you change the baudrate in the sketch, you have to change the baudrate in the serial monitor of the Arduino IDE as well. If the 115200 baud made it worse, then there is something going on that I don't understand.
That led driver seems to run on 3.3V internally. In that case it uses a 3.3V I2C bus.
It seems to be a lot of low level electronics control. The datasheet explains it well, but it is still hard to understand. If you have any questions about I2C, I will be glad to answer them.