some fixes

python_app/hardware_full/librevna_multi_device_driver/controller.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 from collections.abc import Iterator, Sequence
+from contextlib import suppress
 from dataclasses import replace
 from typing import Optional
 import threading
@@ -46,12 +47,15 @@ class MultiDeviceVnaController:
         self._is_closed = False
 
         try:
+            # Register each device the moment it opens so a partial open (e.g. a
+            # slave that fails after the master is up) is fully released by close().
+            # Otherwise the master USB handle and its RX thread leak on every retry.
             self._master_device = LibreVnaUsbBulkConnection(master_serial_number)
-            self._slave_devices = [
-                LibreVnaUsbBulkConnection(slave_serial_number)
-                for slave_serial_number in slave_serial_numbers
-            ]
-            self._all_devices = [self._master_device, *self._slave_devices]
+            self._all_devices.append(self._master_device)
+            for slave_serial_number in slave_serial_numbers:
+                connection = LibreVnaUsbBulkConnection(slave_serial_number)
+                self._slave_devices.append(connection)
+                self._all_devices.append(connection)
         except Exception:
             self.close()
             raise
@@ -65,14 +69,20 @@ class MultiDeviceVnaController:
         self.close()
 
     def close(self) -> None:
-        """Stop sweeping and close every opened device transport."""
+        """Stop sweeping and close every opened device transport.
+
+        Resilient to a half-open or already-broken controller: failing to idle or
+        close one device must not prevent the others from being released.
+        """
         if self._is_closed:
             return
 
         self._is_closed = True
-        self._send_idle_to_all_devices()
+        with suppress(Exception):
+            self._send_idle_to_all_devices()
         for device_connection in self._all_devices:
-            device_connection.close()
+            with suppress(Exception):
+                device_connection.close()
 
     def stop_continuous_sweep(self) -> None:
         """Stop the currently running sweep without closing device transports."""