diff --git a/vna_system/core/processors/configs/bscan_config.json b/vna_system/core/processors/configs/bscan_config.json
index b0a8735..6db4813 100644
--- a/vna_system/core/processors/configs/bscan_config.json
+++ b/vna_system/core/processors/configs/bscan_config.json
@@ -4,7 +4,7 @@
   "s11_norm_enabled": false,
   "subtract_mean_ascan": false,
   "hardcoded_notch_enabled": false,
-  "axis": "real",
+  "axis": "imag",
   "cut": 0.0,
   "max": 3.0,
   "gain": 1.5,
diff --git a/vna_system/core/processors/implementations/bscan_processor.py b/vna_system/core/processors/implementations/bscan_processor.py
index 2111f28..7ae50ec 100644
--- a/vna_system/core/processors/implementations/bscan_processor.py
+++ b/vna_system/core/processors/implementations/bscan_processor.py
@@ -512,7 +512,6 @@ class BScanProcessor(BaseProcessor):
             y_coords: list[float] = []
             z_values: list[float] = []
 
-            z_values_square = np.zeros((len(history[0]["distance_data"]),len(history)),dtype=float)
             time_series = [record["time_domain_data"] for record in history]
             adjusted_time_series = self._apply_mean_ascan_subtraction(time_series)
 
@@ -525,7 +524,6 @@ class BScanProcessor(BaseProcessor):
                     normalized_ampls = np.array(amps) / np.max(np.array(amps)[depth_mask])
                 else:
                     normalized_ampls = np.array(amps)
-                z_values_square[:,sweep_index-1] = normalized_ampls
 
                 for d, a in zip(depths, normalized_ampls, strict=False):
                     x_coords.append(sweep_index)
diff --git a/vna_system/core/processors/websocket_handler.py b/vna_system/core/processors/websocket_handler.py
index 14f0955..6f9514e 100644
--- a/vna_system/core/processors/websocket_handler.py
+++ b/vna_system/core/processors/websocket_handler.py
@@ -71,6 +71,7 @@ class ProcessorWebSocketHandler:
             
         await websocket.accept()
         self.active_connections.add(websocket)
+        self._send_locks[websocket] = asyncio.Lock()
         logger.info("WebSocket connected", total_connections=len(self.active_connections))
 
         try:
@@ -87,8 +88,22 @@ class ProcessorWebSocketHandler:
         """Remove a connection and log the updated count."""
         if websocket in self.active_connections:
             self.active_connections.remove(websocket)
+            self._send_locks.pop(websocket, None)
             logger.info("WebSocket disconnected", total_connections=len(self.active_connections))
 
+    async def _send(self, websocket: WebSocket, message_str: str) -> None:
+        """
+        Send text on a connection, serialized against any other send on it.
+
+        All outbound traffic must go through here; see `_send_locks`.
+        """
+        lock = self._send_locks.get(websocket)
+        if lock is None:
+            # Connection already torn down.
+            return
+        async with lock:
+            await websocket.send_text(message_str)
+
     # --------------------------------------------------------------------- #
     # Inbound messages
     # --------------------------------------------------------------------- #
@@ -96,7 +111,7 @@ class ProcessorWebSocketHandler:
         """Parse and route an inbound client message."""
         # Handle ping/pong messages first (they are not JSON)
         if data == "ping":
-            await websocket.send_text("pong")
+            await self._send(websocket, "pong")
             return
         elif data == "pong":
             # Just acknowledge, no response needed
@@ -189,7 +204,7 @@ class ProcessorWebSocketHandler:
                     for r in history
                 ],
             }
-            await websocket.send_text(json.dumps(response))
+            await self._send(websocket, json.dumps(response))
         except Exception as exc:  # noqa: BLE001
             logger.error("Error getting history")
             await self._send_error(websocket, f"Ошибка получения истории: {exc}")
@@ -270,7 +285,7 @@ class ProcessorWebSocketHandler:
 
         try:
             response = await asyncio.to_thread(self.processor_manager.build_processor_state, processor_id)
-            await websocket.send_text(json.dumps(response))
+            await self._send(websocket, json.dumps(response))
         except Exception as exc:  # noqa: BLE001
             logger.error("Error getting processor state", processor_id=processor_id, error=repr(exc))
             await self._send_error(websocket, f"Ошибка получения состояния процессора: {exc}")
@@ -371,7 +386,7 @@ class ProcessorWebSocketHandler:
             if raw_data:
                 payload["raw_data"] = raw_data
 
-            await websocket.send_text(json.dumps(payload))
+            await self._send(websocket, json.dumps(payload))
         except Exception as exc:  # noqa: BLE001
             logger.error("Error sending error message", error=repr(exc))
 
@@ -432,7 +447,7 @@ class ProcessorWebSocketHandler:
         disconnected: list[WebSocket] = []
         for websocket in list(self.active_connections):  # snapshot
             try:
-                await websocket.send_text(message_str)
+                await self._send(websocket, message_str)
             except Exception as exc:  # noqa: BLE001
                 logger.error("Broadcast to client failed; marking for disconnect", error=repr(exc))
                 disconnected.append(websocket)
diff --git a/vna_system/main.py b/vna_system/main.py
index 676b364..f42cb48 100644
--- a/vna_system/main.py
+++ b/vna_system/main.py
@@ -103,6 +103,11 @@ def main() -> None:
         # (hundreds of sweeps x 1000 points each easily exceeds it); the
         # connection is silently reset with no application-level error.
         ws_max_size=256 * 1024 * 1024,
+        # The client drives its own ping/pong (see web_ui websocket.js), and the
+        # library's keepalive task races with our large result frames on the same
+        # transport, tripping an assertion inside websockets' drain handling.
+        ws_ping_interval=None,
+        ws_ping_timeout=None,
     )