This is a known issue. Basically, the neopixel module and ESP32's underlying RTOS do not play well together. There are ways to circumvent this. One being the use of the RMT facility. See this thread
This is a known issue. Basically, the neopixel module and ESP32's underlying RTOS do not play well together. There are ways to circumvent this. One being the use of the RMT facility. See this thread