diff --git a/src/socket/socketmanager.js b/src/socket/socketmanager.js
index 4e52da0..5639730 100644
--- a/src/socket/socketmanager.js
+++ b/src/socket/socketmanager.js
@@ -23,6 +23,7 @@ export class SocketManager {
     // Create Socket.IO server - CORS applies to HTTP long-polling transport
     const allowedOrigins = config.server.corsOrigins || ['*'];
     const io = new Server(server, {
+      maxHttpBufferSize: 1e8,
       cors: {
         origin: (origin, callback) => {
           // Allow requests with no origin (e.g. same-origin, Postman, native apps)
diff --git a/src/socket/socketuser.js b/src/socket/socketuser.js
index 48335b4..655cbff 100644
--- a/src/socket/socketuser.js
+++ b/src/socket/socketuser.js
@@ -306,23 +306,41 @@ export class SocketUser {
   }
 
   async handlePreviewTemplateEvent(data, callback) {
-    const result = await this.templateManager.renderTemplate(
-      data._id,
-      data.content,
-      data.testObject,
-      data.scale
-    );
-    callback(result);
+    try {
+      const result = await this.templateManager.renderTemplate(
+        data._id,
+        data.content,
+        data.testObject,
+        data.scale
+      );
+      if (typeof callback === 'function') {
+        callback(result);
+      }
+    } catch (err) {
+      logger.error('Preview template event error:', err);
+      if (typeof callback === 'function') {
+        callback({ error: err.message });
+      }
+    }
   }
 
   async handleRenderTemplatePDFEvent(data, callback) {
-    const result = await this.templateManager.renderPDF(
-      data._id,
-      data.content,
-      data.object,
-      1
-    );
-    callback(result);
+    try {
+      const result = await this.templateManager.renderPDF(
+        data._id,
+        data.content,
+        data.object,
+        1
+      );
+      if (typeof callback === 'function') {
+        callback(result);
+      }
+    } catch (err) {
+      logger.error('Render template PDF event error:', err);
+      if (typeof callback === 'function') {
+        callback({ error: err.message });
+      }
+    }
   }
   async handleGenerateHostOtpEvent(data, callback) {
     const result = await generateHostOTP(data._id);
diff --git a/src/templates/templatemanager.js b/src/templates/templatemanager.js
index 66d2e7c..e262f95 100644
--- a/src/templates/templatemanager.js
+++ b/src/templates/templatemanager.js
@@ -407,6 +407,9 @@ export class TemplateManager {
       } else {
         const objectType = documentTemplate?.objectType;
         const model = getModelByName(objectType);
+        if (model == null) {
+          return { error: `Unknown object type: ${objectType}` };
+        }
         const defaultKeys = Object.keys(model.schema.obj);
         const defaultValues = {};
         for (const key of defaultKeys) {