Freezing ESP8266 after 4-8h

Build my own 'Artnet to WS2812b Neopixel' boxes for lighting in a club. Working fine. I have 20 stripes with 50 pxls each. One ESP8266(NodeMCU) is feeding 6 stripes, so it gets 2 DMX universes via Artnet. Depending on the FPS(~20-40FPS) i'm sending, thats about 200-300kbp/s constant bitrate for each of the ESPs. Every 4-8h one of my boxes freezes randomly. No pinging possible anymore. The other boxes continue working as usual. Only chance of resetting is to disconnect the power. First, i thought the ESP gets to hot (installed at the clubs ceeling and the power supply is also in such a box) or the humidity is to high, but it must be a software problem (tested it in the oven, dont laugh ;)). So why isn't the watchdog resetting? I am not able to provoke any of those freezes at home (only waiting)

The code is pretty straight forward:

1. test the leds

2. connect to wifi (if no wifi, go to 1)

Loop:

3. check UDP packets for Artnetdata

4. update the WS2812 with the fastled-lib

any ideas?

#define FASTLED_ESP8266_NODEMCU_PIN_ORDER
#include <ESP8266WiFi.h>
#include <WiFiUdp.h>

#include <FastLED.h>

// ARTNET CODES
#define ARTNET_DATA 0x50
#define ARTNET_POLL 0x20
#define ARTNET_POLL_REPLY 0x21
#define ARTNET_PORT 6454
#define ARTNET_HEADER 17

WiFiUDP udp;

#define NUM_LEDS 50

CRGB leds[NUM_LEDS];
CRGB leds2[NUM_LEDS];
CRGB leds3[NUM_LEDS];
CRGB leds4[NUM_LEDS];
CRGB leds5[NUM_LEDS];
CRGB leds6[NUM_LEDS];


unsigned long previousMillis = 0;
int offset=0;

uint8_t uniData[514];
uint8_t maxuni=0;
uint16_t uniSize;
uint8_t hData[ARTNET_HEADER + 1];


const char* ssid     = "*";
const char* password = "*";

IPAddress local_ip(192, 168, 0, 111);
IPAddress gateway_ip(192, 168, 0, 1);
IPAddress subnet_ip(255, 255, 255, 0);

void setup() {
  WiFi.begin(ssid, password);
  WiFi.config(local_ip, gateway_ip, subnet_ip);

  while (WiFi.status() != WL_CONNECTED) {
   delay(500);


delay(2000); // sanity delay
FastLED.addLeds<WS2812, 1, GRB>(leds, NUM_LEDS);
FastLED.addLeds<WS2812, 2, GRB>(leds2, NUM_LEDS);
FastLED.addLeds<WS2812, 3, GRB>(leds3, NUM_LEDS);
FastLED.addLeds<WS2812, 4, GRB>(leds4, NUM_LEDS);
FastLED.addLeds<WS2812, 5, GRB>(leds5, NUM_LEDS);
FastLED.addLeds<WS2812, 6, GRB>(leds6, NUM_LEDS);
initTest();

  }

  udp.begin(ARTNET_PORT); // Open ArtNet port
}

void loop() {

  if (udp.parsePacket()) { 
    udp.read(hData, ARTNET_HEADER+1);
    if ( hData[0] == 'A' && hData[1] == 'r') { //checking first two letters, if its Artnet data
      if ( hData[8] == 0x00 && hData[9] == ARTNET_DATA) {
      uniSize = (hData[16] << 8) + (hData[17]);
      udp.read(uniData, uniSize);

      if(hData[14]>maxuni){maxuni=hData[14];}

     switch(hData[14]+1-maxuni){

      case 0: //for each DMX universe updating the pixels
         for (int j=50; j--;){
            leds[j].setRGB(uniData[j*3+offset],uniData[j*3+1+offset],uniData[j*3+2+offset]);
          leds2[j].setRGB(uniData[j*3+150+offset],uniData[j*3+151+offset],uniData[j*3+152+offset]);
          leds3[j].setRGB(uniData[j*3+300+offset],uniData[j*3+301+offset],uniData[j*3+302+offset]);
         }
         break;

      case 1:
         for (int j=50; j--;){
           leds4[j].setRGB(uniData[j*3+offset],uniData[j*3+1+offset],uniData[j*3+2+offset]);
          leds5[j].setRGB(uniData[j*3+150+offset],uniData[j*3+151+offset],uniData[j*3+152+offset]);
          leds6[j].setRGB(uniData[j*3+300+offset],uniData[j*3+301+offset],uniData[j*3+302+offset]);
         }
         break;
     }
}
}
}

FastLED.show();
}


void initTest()
{
//only at Startup checking the LEDs, so nothing special here....}