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Fixed in 2018.3.X

Fixed in 5.5.X, 5.6.X, 2017.1.X, 2017.2.X, 2018.1.X, 2018.2.X



Found in



Issue ID




Unity throws out Fatal Error: Callback registration failed kMaxCallback



Unity throws out Fatal Error: "Callback registration failed kMaxCallback" after working with the project for 30 minutes or more. It appears randomly.

1. Actively use Unity for more than 30 minutes

Actual: Unity continues to work
Result: Unity crashes with Fatal Error.

Reproducible with: 2017.1.4f1, 2017.2.3p1, 2017.4.4f1, 2018.1.3f1, 2018.2.0b6

Reproduced on macOS, Windows, Linux.
Bug Report window does not appear.
Scene files are not restored after reopening Unity so all not saved Scenes are lost.

  1. karl_jones

    Jan 04, 2019

    Please file a new bug report If you are still encountering this problem. The error message is a symptom and can be caused by many different areas. The area for this bug has been fixed.

Comments (202)

  1. maxsun

    Jul 29, 2017 23:38

    same win10 2017 f3

  2. JannickL

    Jul 29, 2017 22:16

    Same for me. Win 10 and Unity 2017.1.0f3.

  3. iDeveloper2

    Jul 29, 2017 12:50

    I also facing this issue in unity 2017.1.0f3

  4. Johngun

    Jul 29, 2017 11:27

    Same here, plus all work is lost, macOS 10.12.5, unity 2017.1.0f3

  5. Gri94

    Jul 28, 2017 14:29

    Same problem, Windows 10, unity 2017.1.0f3

  6. polycube

    Jul 28, 2017 00:46

    I have same problem. It happens almost every two hours...........

  7. sevensails

    Jul 27, 2017 19:09

    I have the exact same problem!

  8. NRF

    Jul 27, 2017 14:08

    Same problem here (Unity 2017.1.0f3, Win10 [resettet my OS 2 weeks ago from win8 to win10]).
    Last 15 times it happens after changing some .cs when pressing the Play button (between 3h and 30min). But 1 time (last one) it happend after i drag and dropped a prefab from an other project to my project, then i grabbed the prefab in Unity and wanted to drag and drop it into the hierachy, but after dragging it it crashed.

  9. Laniemme

    Jul 26, 2017 23:40

    I keep getting this occasionally too. I will press play, the dialog box appears, I click Quit and...well you can guess what happens next. Windows 10, Unity 2017.1.0f3. I'm glad I have an autosave asset so I don't lose any work.

  10. Racsoth

    Jul 26, 2017 19:38

    +1 on this. Version: 2017.1.0f3. Has happened several times to me, randomly after pressing the Play button. Bug reporting window doesn't appear.

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