Why are there two music managers after I revisit room 1?

You marked the object Persistent and also placed it in the room. When you re-enter the room, GameMaker creates the room-instance even though the persistent one already exists. Singleton check on Create prevents the duplicate.

What's a singleton check?

In the object's Create event: if (instance_number(object_index) > 1) { instance_destroy(); exit; }. The first instance survives; subsequent duplicates self-destroy on creation.

Should I avoid placing persistent objects in rooms?

Yes. Create them once from a controller object's Game Start event. They persist and don't get re-created on room change.

Fix: GameMaker Persistent Object Duplicated on Room Re-entry

Quick answer: Add a singleton check in the object’s Create event: if more than one exists, destroy this. Or never place persistent objects in rooms — create from a Game Start controller.

Music manager runs fine in room 1. Player exits to room 2, returns to room 1. Two music tracks play simultaneously because both the original persistent instance and the new room-placed instance exist.

The Symptom

Persistent object accumulates duplicates each time you re-enter its placement room. Over time, dozens of copies running.

The Fix

Singleton check in Create.

/// In obj_music_manager Create event

if (instance_number(object_index) > 1) {
    instance_destroy();
    exit;
}

// First instance: do setup
audio_play_sound(snd_main_theme, 10, true);

If a duplicate already exists, the new one destroys itself before doing any setup. Original keeps running.

Or: don’t place persistent objects in rooms.

/// In obj_controller Create (placed in start-up room only)
if (!instance_exists(obj_music_manager)) {
    instance_create_layer(0, 0, "Instances", obj_music_manager);
}

Create once from the start-up controller. Persistence keeps it across rooms; no room placements duplicate.

Verifying

Travel back and forth between rooms. instance_number(obj_music_manager) should stay at 1. show_debug_message it from a Step event during dev to confirm.

“Singleton check or controller-spawn. Persistent stays one.”

Related Issues

For instance_deactivate, see deactivate region. For surface lost, see surface lost.

Check on Create. Or never room-place. One instance.