diff --git a/custom_components/nvidia_shield/media_player.py b/custom_components/nvidia_shield/media_player.py
index 37e308e..b9164ab 100644
--- a/custom_components/nvidia_shield/media_player.py
+++ b/custom_components/nvidia_shield/media_player.py
@@ -129,6 +129,23 @@ async def _migrate_legacy_unique_id(hass, entry) -> None:
             _name, new_id = info
     if not new_id:
         new_id = entry.entry_id
+    # t26 F4: another entry may already own the target MAC — the collision
+    # pre-check falls back to the config-entry id instead of re-binding the
+    # unique_id to a MAC that could collide with a real second instance.
+    other_entries = getattr(
+        getattr(hass, "config_entries", None), "entries", []
+    ) or []
+    if any(
+        getattr(other, "unique_id", None) == new_id
+        for other in other_entries
+        if getattr(other, "entry_id", None) != entry.entry_id
+    ):
+        _LOGGER.warning(
+            "P5-1: unique_id migration target %r already in use — falling "
+            "back to the config-entry id",
+            new_id,
+        )
+        new_id = entry.entry_id
     hass.config_entries.async_update_entry(entry, unique_id=new_id)
     _LOGGER.info("P5-1: legacy unique_id %r migrated to %r", legacy, new_id)