ENS160 sensor not working properly when using WiFi simultaneously on ESP8266

Question

I have a problem with the ENS160 air quality sensor. I hooked it up to an ESP8266 via I2C (0x53) and it worked perfectly fine, until I started using WiFi simultaneously. The communicating with the ENS160 is still possible. However, instead of transmitting useful data (like it did before), it just sends the value 0 back and I just can't figure out why. It seems like the problem occurs as soon as i call WiFi.begin(), because the ENS160 sends useful data before that line. Could It be that there is a problem with interrupts? But the I2C communication should still work. The BME280 sensor that I connected via I2C as well, still works perfectly fine. The WiFi connection itself works perfectly fine as well.

Here is the code:

#include <Wire.h> //I2C
#include <Adafruit_Sensor.h> //BME280
#include <Adafruit_BME280.h> //BME280
#include <ScioSense_ENS160.h> //ENS160
#include <ESP8266WiFi.h> //WiFi
#include <ESP8266HTTPClient.h> //WiFi
#include <WiFiClient.h> //WiFi


#define USE_ENS160 //Use ENS160

//Sensors
Adafruit_BME280 bme; //Create a bme object (I2C interface)
#ifdef USE_ENS160
  ScioSense_ENS160 ens160(ENS160_I2CADDR_1); //Create a ens160 object with the I2C-Address 0x53
#endif


//Network
const char* ssid = "ssid"; //Network SSID
const char* password = "password"; //Network Password

const char* serverPath = "path"; //The server domain and path where the sensor data is posted

//Sensor data variables
float temperature = 0.0; //The current temperature (°C)
float humidity = 0.0; //The current humidity (%)
float pressure = 0.0; //The current barometric pressure (hPa)
int co2 = 0; //The current CO2 values (parts per million)

unsigned long lastTime = 0;
unsigned long timerDelay = 5000;

//Prototypes
//void blinkLedErrorLoop

void setup() {

  //PinModes
  pinMode(LED_BUILTIN, OUTPUT); //The internal LED is an output

  //Start the serial connection
  Serial.begin(115200); //Start the serial monitor with a baud rate of 115200 bps
  Serial.println("\nCO2 sensor program started..."); //Print to check if the serial connection works

  //Init the BME sensor
  Serial.println("Initializing BME280...");
  bool bmeStatus = bme.begin(0x76); //Start the I2C-Communication with the bme on address 0x76 and save the status of the initialization in bmeStatus
  
  //Check if the connection was sucessful
  if(!bmeStatus){ //Error -> Could not connect to BME280
    Serial.println("ERROR: Could not connect to BME280. Check the connection and restart the Controller!");
    blinkLedErrorLoop(); //Endless error loop
  }

  Serial.println("Initialization of BME280 complete.");


  //Init the ENS160 CO2 etc. sensor
  #ifdef USE_ENS160
    ETS_GPIO_INTR_ENABLE();
    Serial.print("Initializing ENS160...");

    ens160.begin(); //Begin the communication with the ENS160

    bool ensStatus = ens160.available(); //Is the ENS160 available? yes: true, no: false 
    if(!ensStatus){ //Error -> Could not connect to ENS160
      Serial.println("ERROR: Could not connect to ENS160. Check the connection and restart the..)
      blinkLedErrorLoop(); //Endless error loop
    }
    
    //Connection sucessful -> print ENS160 versions
    Serial.print("\tRev: "); Serial.print(ens160.getMajorRev());
    Serial.print("."); Serial.print(ens160.getMinorRev());
    Serial.print("."); Serial.println(ens160.getBuild());
    Serial.print("\tStandard mode ");
    Serial.println(ens160.setMode(ENS160_OPMODE_STD) ? "done." : "failed!");
    
    Serial.println("Initialization of ENS160 complete.");
  #endif

  connectToWiFi(); //Connect to the network
}

void loop() {

  if((millis() - lastTime) > timerDelay){

  
    //Read the values from the BME280
    readBMEValues(); //Read the sensor values from the BME280
    printBMEValuesToConsole(); //Print the values from the BME280 to the console

    //Read the values from the ENS160
    #ifdef USE_ENS160
      if (ens160.available()) {
      ens160.measure(true);
      ens160.measureRaw(true);

      readENSValues(); //Read the sensor values from the ENS160
      printENSValuesToConsole(); //Print the sensor values from the ENS160 to the console
      }
    #endif
  
    //Send the sensor data to the server
    bool sendingSuccessful = postSensorData();

    lastTime = millis();
  }

}



void blinkLedErrorLoop(){
  bool ledOnOff = true; //Write the internal LED HIGH (true) or LOW (false)
  
  while(1){ //Endless loop
    ledOnOff = !ledOnOff; //Toggle HIGH and LOW
    digitalWrite(LED_BUILTIN, ledOnOff); //Write the LED HIGH or LOW
    delay(500); //Wait for 1s
  }
}

//Read the sensor values from the BME280
void readBMEValues(){
  Serial.println("Reading the values from the BME280...");
  temperature = bme.readTemperature(); //Read the temperature
  humidity = bme.readHumidity(); //Read the humidity
  pressure = bme.readPressure() / 100.0f;
}

//Print the sensor readings from the BME280 to the console
void printBMEValuesToConsole(){
  Serial.println("Temperature: " +  (String)temperature + "°C, Humidity: " + (String)humidity + "%, Pressure: " + (String)pressure + "hPa"); //Print the values of the BME280 to the console
}

#ifdef USE_ENS160
  //Read the sensor values from the ENS160
  void readENSValues(){
    Serial.println("Reading the values from the ENS160...");
    co2 = ens160.geteCO2(); //Read the CO2 value
  }

  //Print the sensor readings from the ENS160 to the console
  void printENSValuesToConsole(){
    Serial.println("CO2: " + (String)co2 + "ppm");
  }
#endif

void connectToWiFi(){
  WiFi.begin(ssid, password); //Connect to the network
  
  Serial.print("Connecting to WiFi");
  while(WiFi.status() != WL_CONNECTED){ //Print dots while not connected
    Serial.print(".");
    delay(500); //Wait half a second
  }

  Serial.println("\nConnected to network! IP: " + WiFi.localIP().toString() + ", Subnet mask: " + WiFi.subnetMask().toString() + ", Gateway: " + WiFi.gatewayIP().toString()); //Connection sucessful. Print IP address, subnet mask and gateway ip
}

void disconnectFromWiFi(){
  Serial.print("Diconnecting from WiFi");
  
  WiFi.disconnect(); //Disconnect and turn off WiFi
  
  while(WiFi.status() == WL_CONNECTED){
    Serial.print(".");
    delay(500);
  }
  Serial.println("\nDisconnecting from WiFi sucessful.");
  WiFi.mode(WIFI_OFF);

}
//Send the sensor data to the specified webserver using the post method and json format
bool postSensorData(){
  if(WiFi.status() == WL_CONNECTED){ //Connected to the network
    WiFiClient client; //WiFi client
    HTTPClient http; //Http request client
    http.begin(client, serverPath); //Begin a http request

    http.addHeader("Content-Type", "application/json"); //Specify that the data format is json

    //Specify the request data
    //JSON format: {"key1":"value1", "key2":"value2", ...}
    String requestDataJSON = "{\"mac_address\":\"" + WiFi.macAddress() + "\","; //Add the mac_address (unique id) to the request
    requestDataJSON += "\"co2\":\"" + (String)co2 + "\","; //Add the co2 sensor value to the request
    requestDataJSON += "\"temperature\":\"" + (String)temperature + "\","; //Add the temperature sensor value to the request
    requestDataJSON += "\"humidity\":\"" + (String)humidity + "\"}"; //Add the humidity sensor value to the request

    Serial.println("Sending JSON: " + requestDataJSON); //Print the request string
    
    int httpResponseCode = http.POST(requestDataJSON); //Send the request with the JSON sensor data
    
    Serial.println("Request sent! Response code: " + (String)httpResponseCode); //Print the response code

    http.end(); //End the http request

    return true;
  }
  else{ // ERROR: Not connected to the network
    return false;
  }
}

The serial output looks like this:

Initializing BME280...
Initialization of BME280 complete.
Initializing ENS160...  Rev: 5.4.6
Standard mode done.
Initialization of ENS160 complete.
Connecting to WiFi.......
Connected to network! IP: 192.168.77.128, Subnet mask: 255.255.255.0, Gateway: 192.168.77.9
Reading the values from the BME280... Temperature: 21.88°C, Humidity: 43.15%, Pressure: 986.26hPa
Reading the values from the ENS160...
CO2: 0ppm
Sending JSON:{"mac_address":"40:91:51:45:21:15","co2":"0","temperature":"21.88","humidity":"43.15"} Request sent! Response code: 200

Any help is appreciated :) Thank you in advance!