some fixes

python_app/hardware_full/librevna_driver/transport/usb.py

@@ -157,8 +157,19 @@ class USBTransport:
         logger.debug("USB disconnect requested")
         self._stop_event.set()
 
-        if self._rx_thread is not None and self._rx_thread.is_alive():
-            self._rx_thread.join(timeout=1.0)
+        rx_thread = self._rx_thread
+        if rx_thread is not None and rx_thread.is_alive():
+            rx_thread.join(timeout=1.0)
+            if rx_thread.is_alive():
+                # The RX thread is wedged inside libusb; closing the handle or
+                # context now would risk a use-after-free in the still-running
+                # bulkRead. Deliberately leak both rather than crash the process.
+                logger.error(
+                    "USB RX thread did not stop within timeout; leaking USB handle/context "
+                    "to avoid use-after-free (serial=%s)",
+                    self.connected_serial,
+                )
+                return
         self._rx_thread = None
 
         if self._handle is not None: