diff --git a/src/gui/main_window.py b/src/gui/main_window.py
index 2081c88..bd13a96 100644
--- a/src/gui/main_window.py
+++ b/src/gui/main_window.py
@@ -1436,11 +1436,10 @@ class MainWindow(ctk.CTk):
                     else:
                         self._sub_step_frame.set_phase("error")
 
-                # Step 4: mark sub-steps based on result
+                # Step 4: sub-steps already marked individually inside _run_step_4;
+                # avoid set_phase which would restart a pulse on Boot Verify.
                 if i == 3 and hasattr(self, '_tftp_sub_step_frame'):
-                    if success:
-                        self._tftp_sub_step_frame.set_phase("Boot Verify")
-                    else:
+                    if not success:
                         self._tftp_sub_step_frame.set_step_error("Boot Verify")
             except Exception as e:
                 results.append(False)