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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. TiagoSerra

    Aug 04, 2017 03:16

    Same here on both clean install of OSX Sierra latest update and also latest 64 bit windows 10

  2. gss214

    Aug 04, 2017 00:02

    same here. win10 64bits and unity 2017.1.0f3

  3. DavidErosa

    Aug 03, 2017 15:12

    Same with Windows 10 64 bita and Unity 2017.1.0f3. Editor closes and no bug report dialog. I can't find a way to reproduce it but for me it's always when I enter Play mode after coming back from Visual Studio.

  4. VishalFbs

    Aug 03, 2017 11:55

    Facing same issue for window 8 and unity 2017.1.0f

  5. Ashwin-Star

    Aug 02, 2017 19:26

    Fatal Error! > Callback registration failed. Increase kMaxCallback.

  6. Ashwin-Star

    Aug 02, 2017 19:24

    happened twice so far, once when Played the scene another when switched from Mono to Unity. ver 2017.1.0f3

  7. zapposh

    Aug 01, 2017 10:41

    Also happens in 2017.1 p2

  8. bc-maia

    Jul 30, 2017 02:35

    well, it started here. In my case it happens when I left the editor idle for some time while working on Visual Studio, then when I return to the editor screen it dies.

  9. Mr-Knieves

    Jul 30, 2017 02:02

    2017.1.0f3 MacOS Sierra.

  10. Mr-Knieves

    Jul 30, 2017 02:00

    Keeps happening to me randomly. Not sure what is triggering it.

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