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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. fuzzygoat

    Jul 19, 2018 15:03

    My Unity 2018.2.0f2 crashes this morning were on macOS High Sierra 10.13.6 (17G65)

  2. fuzzygoat

    Jul 19, 2018 15:01

    Same here in Unity 2018.2.0f2, crashed twice this morning, lost about 30mins unsaved work, very annoying.

  3. Jared-Vargason

    Jul 18, 2018 22:17

    I've gotten this twice on 2018.2.0f2 (Windows) in the last week or so. My experience was like that of AMISNER2K

  4. JimeoWan

    Jul 18, 2018 11:19

    I also have it occasionnally on 2018.2.0f2 (Windows).

  5. melting_pot

    Jul 17, 2018 08:06

    Just got this in 2018.2.0f2 after editing a script and clicking play in the editor.

  6. td-lambda

    Jul 15, 2018 06:59

    I can also confirm this is still happening in 2018.2.0f2

  7. amisner2k

    Jul 14, 2018 07:57

    For me it happened while recompiling scripts after having just saved a script in Visual Studio and alt-tabbing back to Unity...during my session I had made frequent tests in Play Mode (clicking the Play button a lot)...after about 30 or so minutes...the issue occurred.

  8. amisner2k

    Jul 14, 2018 07:53

    This also just happened for me on 2018.2.0f2

  9. AA-Matt

    Jul 14, 2018 07:35

    Also just got this on 2018.2.0f2

  10. ZenithSal

    Jul 13, 2018 13:30

    Issue just happened in 2018.2.0f2, so still here.

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