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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. sbrodie

    Jul 14, 2017 17:59

    Happening regularly on Unity 2017.1.0f3, both new and upgraded projects.

  2. darthbator

    Jul 14, 2017 08:47

    This issue is not fixed I am still encountering it as well

  3. Cynikal

    Jul 14, 2017 06:30

    Just happened to be in the latest release of 2017.1.0f3

  4. ventedpennies

    Jul 14, 2017 04:22

    This is not fixed for 2017. I have never received this error, now I receive it on a regular basis.

  5. RafayAli

    Jul 13, 2017 12:12

    Its happening ever since I installed 2017.1, never happened even once when using previous versions.

  6. ReneBuehling

    Jul 12, 2017 17:27

    This is NOT resolved. It still happens in 2017.1.0f3 (64-bit)

    Actually it happens even *since* I am using 2017.1, and did not happen before. :(

  7. Atticite

    Jul 11, 2017 19:38

    Just encountered this one in 2017.1.0f3, so not entirely fixed ...

  8. fogsight

    Jul 02, 2017 01:27

    "Fatal Error!
    Callback registration failed. Increase kMaxCallback."
    Unity 2017.1.0f1
    Happens sporadically. Last time on Alt-Tab back when left running scene in Play mode.

  9. Lepascal

    Jun 20, 2017 10:38

    Idem in Mac Unity 2017.1.0.B9.

  10. himzy

    Jun 18, 2017 14:54

    Still happening

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