diff --git a/api/config_routes.py b/api/config_routes.py
index 3c8e1d7..dd39fb6 100644
--- a/api/config_routes.py
+++ b/api/config_routes.py
@@ -226,6 +226,8 @@ async def update_setting_endpoint(request):
 
         if not key or value is None:
             return await handle_api_error(request, "Missing 'key' or 'value' in request", 400)
+        if key not in _SETTINGS_FIELDS:
+            return await handle_api_error(request, f"Unknown setting: {key}", 400)
 
         config = load_config()
         if 'settings' not in config:
@@ -254,7 +256,10 @@ async def update_master_endpoint(request):
         if "name" in data:
             config['master']['name'] = data['name']
         if "host" in data:
-            config['master']['host'] = data['host']
+            if data["host"] is None:
+                config['master'].pop('host', None)
+            else:
+                config['master']['host'] = normalize_host(data["host"])
         if "port" in data:
             config['master']['port'] = data['port']
         if "cuda_device" in data:
diff --git a/nodes/collector.py b/nodes/collector.py
index e790298..3e0c205 100644
--- a/nodes/collector.py
+++ b/nodes/collector.py
@@ -52,7 +52,7 @@ class DistributedCollectorNode:
 
         if not multi_job_id or pass_through:
             if pass_through:
-                print(f"[Distributed Collector] Pass-through mode enabled, returning images unchanged")
+                debug_log("Collector: pass-through mode enabled, returning images unchanged")
             return (images, audio if audio is not None else empty_audio)
 
         # Use async helper to run in server loop
diff --git a/nodes/queue_node.py b/nodes/queue_node.py
index 539178c..d7259cc 100644
--- a/nodes/queue_node.py
+++ b/nodes/queue_node.py
@@ -94,8 +94,8 @@ class DistributedQueueNode:
 
     async def _fetch_worker_statuses(self, workers):
         session = await get_client_session()
-        statuses = []
-        for worker in workers:
+        
+        async def _probe(worker):
             url = build_worker_url(worker, "/prompt")
             try:
                 async with session.get(
@@ -103,17 +103,18 @@ class DistributedQueueNode:
                     timeout=aiohttp.ClientTimeout(total=3),
                 ) as resp:
                     if resp.status != 200:
-                        continue
+                        return None
                     data = await resp.json()
-                    queue_remaining = int(data.get("exec_info", {}).get("queue_remaining", 0))
-                    statuses.append({
+                    return {
                         "worker": worker,
-                        "queue_remaining": queue_remaining,
-                    })
+                        "queue_remaining": int(data.get("exec_info", {}).get("queue_remaining", 0)),
+                    }
             except Exception as e:
                 debug_log(f"DistributedQueue: Worker status check failed ({url}): {e}")
+                return None
 
-        return statuses
+        results = await asyncio.gather(*[_probe(worker) for worker in workers])
+        return [result for result in results if result is not None]
 
     def _select_worker(self, statuses):
         idle_workers = [status for status in statuses if status["queue_remaining"] == 0]