fix UI block issues

src/slic3r/Utils/NetworkAgent.cpp

@@ -139,6 +139,7 @@ void NetworkAgent::set_printer_agent(std::shared_ptr<IPrinterAgent> printer_agen
     // Local copies to allow safe access after releasing the lock.
     // This pattern ensures the objects stay alive (via shared_ptr refcount) even if
     // another thread modifies m_printer_agent or m_printer_callbacks after we unlock.
+    std::shared_ptr<IPrinterAgent> old_printer_agent;
     std::shared_ptr<IPrinterAgent> new_printer_agent;
     PrinterCallbacks callbacks;
 
@@ -152,6 +153,8 @@ void NetworkAgent::set_printer_agent(std::shared_ptr<IPrinterAgent> printer_agen
 
         // Disconnect all callbacks from the old agent
         apply_printer_callbacks(m_printer_agent, callbacks);
+        // Capture the old agent before overwriting so we can disconnect it outside the lock
+        old_printer_agent = m_printer_agent;
         // Take ownership of the incoming agent and update the agent ID
         m_printer_agent = std::move(printer_agent);
         m_printer_agent_id = m_printer_agent->get_agent_info().id;
@@ -164,6 +167,11 @@ void NetworkAgent::set_printer_agent(std::shared_ptr<IPrinterAgent> printer_agen
     }
     // Lock released here - m_agent_mutex is now free for other threads
 
+    // Disconnect the old agent's connections/threads. The cache keeps it alive,
+    // but we release its network resources while it's not the active agent.
+    if (old_printer_agent && old_printer_agent != new_printer_agent)
+        old_printer_agent->disconnect_printer();
+
     // Apply callbacks OUTSIDE the lock to avoid deadlock risk and minimize
     // critical section duration. The local shared_ptr copy ensures the agent
     // cannot be destroyed while we're using it.