Hope this works

api-customer/app.py

@@ -23,13 +23,15 @@ if __name__ == '__main__':
     local_broker = MQTTService(
         local_broker_address,
         local_broker_port,
-        username="pi-1",
+        client_id="customer-api",
+        username="main",
         password="hepl",
     )
 
     api_broker = MQTTService(
         api_broker_address,
         api_broker_port,
+        client_id="customer-api",
         username="customer",
         password="hepl",
     )

api/src/main/java/MqttStarter.java

@@ -2,6 +2,7 @@ import be.naaturel.boardmateapi.common.helpers.Logger;
 import be.naaturel.boardmateapi.services.MqttService;
 import jakarta.annotation.PreDestroy;
 import org.springframework.boot.context.event.ApplicationReadyEvent;
+import org.springframework.context.annotation.Bean;
 import org.springframework.context.event.EventListener;
 import org.springframework.stereotype.Component;
 
@@ -16,7 +17,7 @@ public class MqttStarter {
         this.service = service;
     }
 
-    @EventListener(ApplicationReadyEvent.class)
+    @Bean
     public void start(){
         try {
             setCallback();