Prevent wrong triggering by requiring 2 triggers within 30 seconds to initially react. Hopefully that helps preventing accidental triggers.

src/main.cpp

@@ -100,6 +100,10 @@ const int millisPerSecond=1000;
 long previousMotionMillis=millis();
 short previousState=0;
 long previousNoMoNotifyMinutes=0;
+
+uint repeatTriggerCounter=0;
+const int repeatTriggerResetSeconds=30;
+const short requiredRepeatsToTrigger=1;
 void loop() {
   if (!mqttClient.connected()) {
     reconnect();
@@ -113,13 +117,27 @@ void loop() {
     Serial.print(" previousState: ");
     Serial.println(previousState);
     if (currentState == HIGH) {
-      send_mqtt("motion");
+      if (repeatTriggerCounter >= requiredRepeatsToTrigger) {
+        send_mqtt("motion");  
+      } else {
+        send_mqtt("motion_ignored");
+      }
       digitalWrite(LED_BUILTIN,HIGH);
       previousMotionMillis=millis();
+      repeatTriggerCounter++;
     } 
     previousState = currentState;
   }
 
+  if (
+          (currentState == LOW) 
+        && (repeatTriggerCounter >= requiredRepeatsToTrigger) 
+        && ((millis()-previousMotionMillis)/millisPerSecond >= repeatTriggerResetSeconds)
+     ) {
+    repeatTriggerCounter =0;
+    send_mqtt("motion_repeat_trigger_reset");
+  }
+
   const int secondsPerMinute=60;
   long minutesSinceLastMotion=(millis()-previousMotionMillis)/(millisPerSecond*secondsPerMinute);
   if ((previousNoMoNotifyMinutes != minutesSinceLastMotion) && (0 != minutesSinceLastMotion)) {