diff --git a/src/nodeClass.js b/src/nodeClass.js
index 7706508..2d68845 100644
--- a/src/nodeClass.js
+++ b/src/nodeClass.js
@@ -80,7 +80,7 @@ class nodeClass {
     const availableMachines = Object.values(mg.machines || {}).filter((machine) => {
       // Safety check: ensure machine and machine.state exist
       if (!machine || !machine.state || typeof machine.state.getCurrentState !== 'function') {
-        console.warn(`Machine missing or invalid:`, machine?.config?.general?.id || 'unknown');
+        mg.logger?.warn(`Machine missing or invalid: ${machine?.config?.general?.id || 'unknown'}`);
         return false;
       }
       
@@ -195,67 +195,52 @@ class nodeClass {
     this.node.on(
       "input",
       async (msg, send, done) => {
-            const mg = this.source;
-            const RED = this.RED;
+        const mg = this.source;
+        const RED = this.RED;
+        try {
           switch (msg.topic) {
-            case "registerChild":
-                    //console.log(`Registering child in mgc: ${msg.payload}`);
-                    const childId = msg.payload;
-                    const childObj = RED.nodes.getNode(childId);
-                    
-                    // Debug: Check what we're getting
-                    //console.log(`Child object:`, childObj ? 'found' : 'NOT FOUND');
-                    //console.log(`Child source:`, childObj?.source ? 'exists' : 'MISSING');
-                    if (childObj?.source) {
-                      //console.log(`Child source type:`, childObj.source.constructor.name);
-                      //console.log(`Child has state:`, !!childObj.source.state);
-                    }
-                    
-                    mg.childRegistrationUtils.registerChild(
-                      childObj.source,
-                      msg.positionVsParent
-                    );
-                    
-                    // Debug: Check machines after registration
-                    //console.log(`Total machines after registration:`, Object.keys(mg.machines || {}).length);
-                    break;
-
+            case "registerChild": {
+              const childId = msg.payload;
+              const childObj = RED.nodes.getNode(childId);
+              if (!childObj || !childObj.source) {
+                mg.logger.warn(`registerChild skipped: missing child/source for id=${childId}`);
+                break;
+              }
+              mg.childRegistrationUtils.registerChild(childObj.source, msg.positionVsParent);
+              break;
+            }
             case "setMode":
-              const mode = msg.payload;
-              mg.setMode(mode);
+              mg.setMode(msg.payload);
               break;
-
             case "setScaling":
-              const scaling = msg.payload;
-              mg.setScaling(scaling);
-
+              mg.setScaling(msg.payload);
               break;
-
-            case "Qd":
+            case "Qd": {
               const Qd = parseFloat(msg.payload);
               const sourceQd = "parent";
-
               if (isNaN(Qd)) {
-                return mg.logger.error(`Invalid demand value: ${Qd}`);
+                mg.logger.error(`Invalid demand value: ${msg.payload}`);
+                break;
               }
-
               try {
                 await mg.handleInput(sourceQd, Qd);
                 msg.topic = mg.config.general.name;
                 msg.payload = "done";
                 send(msg);
-              } catch (e) {
-                console.log(e);
+              } catch (error) {
+                mg.logger.error(`Failed to process Qd: ${error.message}`);
               }
               break;
-
+            }
             default:
-              // Handle unknown topics if needed
               mg.logger.warn(`Unknown topic: ${msg.topic}`);
               break;
           }
-          done();
+        } catch (error) {
+          mg.logger.error(`Input handler failure: ${error.message}`);
         }
+        if (typeof done === 'function') done();
+      }
     );
   }
 
@@ -266,7 +251,7 @@ class nodeClass {
     this.node.on("close", (done) => {
       clearInterval(this._tickInterval);
       clearInterval(this._statusInterval);
-      done();
+      if (typeof done === 'function') done();
     });
   }
 }
diff --git a/src/specificClass.js b/src/specificClass.js
index f8ae8d1..728f586 100644
--- a/src/specificClass.js
+++ b/src/specificClass.js
@@ -2,6 +2,10 @@
 const EventEmitter = require("events");
 const {logger,configUtils,configManager, MeasurementContainer, interpolation , childRegistrationUtils} = require('generalFunctions');
 
+/**
+ * Machine group controller domain model.
+ * Aggregates multiple rotating machines and coordinates group-level optimization/control.
+ */
 class MachineGroup {
     constructor(machineGroupConfig = {}) {
 
@@ -50,7 +54,8 @@ class MachineGroup {
     registerChild(child,softwareType) {
         this.logger.debug('Setting up childs specific for this class');
 
-        const position = child.config.general.positionVsParent;
+        // Prefer functionality-scoped position metadata; keep general fallback for legacy nodes.
+        const position = child.config?.functionality?.positionVsParent || child.config?.general?.positionVsParent;
         
        if(softwareType == "machine"){
            // Check if the machine is already registered
@@ -1396,6 +1401,8 @@ async function makeMachines(){
 }
 
 
-makeMachines();
+if (require.main === module) {
+  makeMachines();
+}
 
 //*/