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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. burakkurkcu

    Sep 10, 2017 08:23

    From the release notes of Patch 2017.1.1p1:
    (873467) - Editor : Fixed Callback registration failed kMaxCallback crash when entering playmode.

    At last, it's solved!

  2. yelizyyy

    Sep 09, 2017 12:13

    it occurs every 30 mins. I use Unity 2017.1.1f1. It is a very annoying bug, why don't you fix it?

  3. Lepascal

    Sep 09, 2017 09:44

    Hello, always the same random bug with the Unity 2017.1.1f1 version under Windows 10 x64.

  4. krougeau

    Sep 05, 2017 07:52

    Still occurring in 2017.1.1f1 (9/4/2017 release). I understand a fix is coming in 2017.2 (and is fixed in the current Beta). Just posting this for anyone else who'd hoped that the latest release had solved the problem...

  5. TheOz

    Sep 03, 2017 17:05

    seeing this in 2017.1p5 just lost a couple of hours of work due to this crash.

  6. Salazar

    Sep 03, 2017 11:13

    Patch 2017.1.0p5
    Same here.

  7. SilentParrotStudio

    Aug 31, 2017 14:48

    They fixed the problem in 2017.2.0.b9 (Beta)!!!

  8. su1935

    Aug 30, 2017 16:32

    unity exits automatically many times a day.

  9. letscodestuff

    Aug 28, 2017 03:27

    I just installed Unity today version 2017.1.0p5. I have started watching some tutorials on the site and going through them and appears this happens randomly anytime I alt tab between Unity and Visual Studio. It can happen every 30 minutes to as soon as I start Unity back up and alt tab for the first time.

  10. AlexKostas

    Aug 27, 2017 17:39

    Now it is common for me. It happens at least 6 times a day to me. And I have already lost many hours of work. I have Unity 2017.1. Fix it please!!!

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