Problem mit Interrupt

#include <ESP8266WiFi.h>
#include <PubSubClient.h>

// Wifi Connection
const char* ssid = "xxx";
const char* password = "xxx";

// MQTT Server address
const int mqtt_port = 1983;
const char* mqtt_server = "192.168.178.xx";
//Topics
const char* gate_topic = "Garage/Gate";

const int interruptGate = D7;//D7

WiFiClient espClient;
PubSubClient client(espClient);

void setup() {
  Serial.begin(9600);
  setup_wifi();
  client.setServer(mqtt_server, mqtt_port);
  client.setCallback(callback);
  //Gate In/Out
  pinMode(interruptGate, INPUT_PULLUP);
  //digitalWrite(interruptGate, HIGH);
  attachInterrupt(digitalPinToInterrupt(interruptGate), handleInterruptGate, CHANGE);
}

void setup_wifi() {
  delay(2);
  // We start by connecting to a WiFi network
  Serial.println();
  Serial.println(ssid);

  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }

  Serial.println("");
  Serial.println("WiFi connected");
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());
}

void callback(char* topic, byte* payload, unsigned int length) {
  //Car In
  if (strcmp(topic, gate_topic) == 0) {
   Serial.print("Message arrived\ntopic = ");
   Serial.print(topic);
   Serial.print(" - ");
    String spayload = "";
    for (int i = 0; i < length; i++) {
      spayload = spayload + (char)payload[i];
    }
    Serial.print("payload = " + spayload + "\n");
  }
}

void reconnect() {
  // Loop until we're reconnected
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    // Attempt to connect
    if (client.connect("Combi_Switch")) {
      Serial.println("connected");
    } else {
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
      // Wait 5 seconds before retrying
      delay(5000);
    }
  }
}

ICACHE_RAM_ATTR void handleInterruptGate() {
  static unsigned long last_interrupt_time = 0;
  unsigned long interrupt_time = millis();
  if (interrupt_time - last_interrupt_time > 20)
  {
    int dr = digitalRead(interruptGate); <--- Das funktioniert nicht zuverlässig!
    if(dr == LOW) {
      client.publish(gate_topic, "true", true);
    } else {
      client.publish(gate_topic, "false", true);
    }
    last_interrupt_time = interrupt_time;
  }
}

void loop() {
  if (!client.connected()) {
    reconnect();
  }
  client.loop();
}