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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. UnbornApple

    Jul 25, 2017 01:47

    I am also getting this regularly. 2017.1.0f3

  2. NRF

    Jul 24, 2017 13:48

    Same problem here. After a couple of hours it crashes regularly (when starting the scene), even after i resettet my OS from Win8 to Win10 (Total OS resett). Working on a 2D mobile game with Unity 2017.1.0f3 Personal
    Thank god saving still works here so i have no lost work.

  3. zzgrzyt

    Jul 24, 2017 12:10

    +1, just hit this as well with a freshly upgraded project from 5.6.2f1 to 2017.1.0f3. Free license.
    Hit it after working with the project for about 2 hours or so.

  4. Daphoeno

    Jul 23, 2017 19:50

    only just started having this issue on a new project created in 2017.1.0f3 - The issue happens repeatedly after using for around 30 minutes.

    I have also noticed that a previously made project that was brought into 2017.1.0f3 from a previous build does not suffer from this problem

  5. clyburnw

    Jul 23, 2017 08:33

    Began happening to me after upgrading to 2017.1 . The crash is inevitable, but unpredictable other than it always occurs in play mode.

  6. Derik-Stavast

    Jul 23, 2017 05:48

    This Issue also occurred with me when I was using Unity 2017.1.0f3. I used Unity for about 30 -45 Minutes

  7. bunnyhero

    Jul 23, 2017 05:42

    i'd never seen this before in earlier versions. now seeing it happen to me every 15-20 minutes, in the editor, in version 2017.1.0f3, on macOS 10.12.6

  8. vhailor1980

    Jul 21, 2017 15:13

    I have the same problem. I was working for about 8 hours then it crashed in my face.

  9. RogerDebian

    Jul 21, 2017 00:50

    1. Actively use Unity for more than 30 minutes

    -> Not for me! just happend! I had Unity open more tan 30 minutes, maybe 5 hours.

  10. Frivoloustwist

    Jul 19, 2017 20:14

    I'm having this issue regularly, meaning several times a development session. Right now I'm using very simple 2D physics in a small test project. Nothing more than 3 game objects (sprites), one with a Rigidbody2D and a DistanceJoint2D. Almost no code, just toying with the joint. The last crash was on the removal of a Rigidbody2D from a GO.

    I'm on Unity 2017.1.0f3 on OSX Sierra 10.12.5. I intend to try the project in 5.6.x. We are holding off upgrading for 'real' projects until we are confident the kinks are worked out of 2017.

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