# Debug Unity Scene Restart Bugs by Following Object Lifetimes Trace duplicate listeners, persistent objects, and stale session state in Unity restart bugs, then verify the fix across repeat sessions and a built player. Canonical URL: https://gameskit.ai/blog/unity-scene-restart-bugs Last updated: 2026-10-29 [Unity](https://gameskit.ai/blog#unity) Trace duplicate listeners, persistent objects, and stale session state in Unity restart bugs, then verify the fix across repeat sessions and a built player. [AI Games Kit Editorial](https://gameskit.ai/blog#editorial) Published September 28, 2026 · Updated October 29, 2026 4 min read [← All guides](https://gameskit.ai/blog) Restart bugs often appear only after the game has already worked once. A second music track starts, a reward is applied twice, or the player cannot move after returning from a menu. The important question is what survived the transition and who was supposed to reset it. Consider a fictional arena game where defeating one enemy adds the expected score during the first match but twice that amount after restarting. Follow the score event through object creation, subscription, transition, and cleanup before changing the scoring rule. /01 ## Define what restart actually means Write the exact sequence that reproduces the bug. Restarting a level inside a running player, returning through a menu, and stopping and starting Editor Play mode are different boundaries. Test them separately and record whether the bug requires victory, defeat, pause, or an unfinished animation. Create a tiny transition record containing the previous scene, next scene, session identifier, and reason for the change. Add temporary diagnostic messages only where they answer a specific question. The arena example needs evidence about how many score events were emitted and how many listeners handled each event, not a dump of every update in the game. /02 ## Assign every suspect object a lifetime List the score service, player, spawner, audio owner, and transition controller. For each, decide whether it belongs to the application, a match, or a scene. Unity’s DontDestroyOnLoad preserves designated objects across scene changes, so inspect those intentional survivors alongside the objects recreated by the new scene. Compare the number and identity of each owner before and after the transition. A persistent score service plus a newly spawned replacement is a different defect from one service with duplicate listeners. Avoid solving both with a broad object search and deletion routine. Establish which object should exist and which system has authority to create it. /03 ## Follow subscriptions and unfinished work Trace registration and cleanup as a pair. If a scene object subscribes to a longer-lived event source, inspect what removes that subscription when the object stops participating. Check whether pooled objects follow the same path as destroyed objects. A fix for one lifetime may leave the other unchanged. Also inspect delayed work created before restart: animation completions, queued callbacks, requests, or timers. Give session-owned work a way to recognize that its session ended. In the arena example, an old enemy’s delayed defeat callback should not award points to the next match. Choose cancellation or rejection according to the existing architecture and verify the boundary explicitly. /04 ## Separate Editor persistence from runtime persistence Record the project’s Enter Play Mode settings. Unity documents that disabling domain reload preserves static fields and static event registrations between Play mode sessions. That can explain an Editor-only second-run symptom, but it does not automatically explain a restart inside an already running game. Reproduce the relevant sequence in a built player before declaring the causes equivalent. If the two environments fail for different reasons, keep separate findings and acceptance checks. Do not change the team’s Editor settings merely to hide a missing reset; make the intended startup and session lifecycle clear in the code that owns it. /05 ## Test repeated transitions and interrupted transitions Repeat the same match-to-menu-to-match route and inspect the owner and listener records at each stable point. Trigger restart while a reward animation is still running, then retry from the normal end screen. The expected result is one legitimate score update for one legitimate event and no contribution from the previous match. Check adjacent state such as pause, audio, selected controls, and the current save slot. Remove noisy diagnostics after preserving useful evidence and review the final diff for unrelated lifecycle changes. Report the transition paths and environments tested so a future regression has an exact route to reproduce. Keep this in mind ## Key takeaways - Treat in-game restart, scene transition, and Editor Play mode re-entry as distinct boundaries. - Track object ownership, event subscriptions, and delayed work across the failing transition. - Verify repeated and interrupted restarts without changing the intended scoring or session rules. ## Sources & further reading Consult the source documentation for the version and platform you are working with. - [Unity 6 scripting API: Object.DontDestroyOnLoad](https://docs.unity3d.com/6000.0/Documentation/ScriptReference/Object.DontDestroyOnLoad.html) - [Unity 6 manual: domain reloading](https://docs.unity3d.com/6000.0/Documentation/Manual/domain-reloading.html) Inside the AI Games Kit ## Workflows for your next step - [Unity Debugging](https://gameskit.ai/#roster) - [Game Release Regression Check](https://gameskit.ai/#roster) Explore these agents and skills in the [Games Kit roster](https://gameskit.ai/#roster). Keep building ## More from the field notes [All guides](https://gameskit.ai/blog) [Unity](https://gameskit.ai/blog/unity-release-candidate-checklist) ### A Unity Release Candidate Checklist Built Around Change Risk Review a Unity release candidate using an identified artifact, change-based test coverage, upgrade checks, and an explicit decision about unresolved risks. October 8, 2026 4 min read Read guide [Unity](https://gameskit.ai/blog/unity-game-settings-persistence) ### Make Unity Game Settings Persist and Apply Consistently Trace Unity settings from stored values to runtime behavior, define defaults and apply rules, and test persistence without erasing unrelated player progress. October 7, 2026 4 min read Read guide [Unity](https://gameskit.ai/blog/unity-play-mode-vs-build-bugs) ### Debug a Unity Game That Works in Play Mode but Fails in a Build Compare Unity Editor and player behavior using matching routes, real player logs, build configuration, and one controlled hypothesis at a time. October 6, 2026 4 min read Read guide Put the workflow to work ## Give your next game a focused team. Explore the AI Games Kit’s agents and skills for Unity and browser-game development, from debugging and playtesting to release preparation. [Explore the AI Games Kit](https://gameskit.ai/#pricing) [See how to use it](https://gameskit.ai/start) --- Markdown version of https://gameskit.ai/blog/unity-scene-restart-bugs, from AI Games Kit (https://gameskit.ai). Site index: https://gameskit.ai/llms.txt · Full text: https://gameskit.ai/llms-full.txt · AI usage policy: https://gameskit.ai/ai.txt