What causes the LED strip to flash?

Question

Arduino

Connected WS2811 tape (50 pcs) to Genuino UNO rev.3 Used this sketch changed line 47:

FastLED.addLeds<WS2811, LED_PIN, RGB>(leds, NUM_LEDS);

Naturally changed the number of LEDs and connection ports. In Prismatik, I set everything up as it should, but noticed unpleasant blinking of the lights during operation. With what it can be connected? How to get rid of it?
There is enough power, I tried to connect the computer power supply in the same way - the same way. Still sometimes the colors do not match, and the first 17 LEDs work perfectly. When testing with the FastLED library, all colors were set correctly and no errors were found.
You can see the work on the video: tyk 1 , tyk 2

Answer 1

Well, in general, the number of LEDs and the leg to which they are connected are set in lines 7 and 8, line 47 should not be touched at all.