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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. DefinitelyNotSteffen

    Feb 21, 2020 09:10

    I Still get this error in 2018.2.21f1.

  2. ellend

    Apr 30, 2019 08:22

    Happened to me many times,v2018.2.3f1

  3. Ruufer

    Apr 23, 2019 01:01

    STILL HAPPENING IN 2018.2.0f2

  4. nuToH

    Sep 13, 2018 13:58

    2018.2.7 Not fixed. What to do? Wait for 2018.3?

  5. reuno

    Sep 02, 2018 18:11

    This is becoming annoying.
    Happens on a daily basis now, and has for a month or so (using 2018.2.x.
    I never encountered it before 2018.2 (or so rarely I never noticed it).

  6. stormred1236

    Aug 31, 2018 22:30

    Still the case for me too....

  7. Baraff

    Aug 30, 2018 05:09

    Related but unrelated. I get this same crash message in the log in windows standalone build when I run the build when built with 2018.2.5f1 but it works fine when built with 2018.2.3f1

    Callback registration failed. Increase kMaxCallback.
    (Filename: Line: 191)


    Aug 29, 2018 19:47

    it's still happening regularly on 2018.2.0f2

  9. zornor90

    Aug 29, 2018 00:39

    Still happening on a build with Unity 2018.2.5 - NOT fixed

  10. royrextred

    Aug 26, 2018 14:38

    Still not fixed

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