Search Issue Tracker

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. Barries19

    Jun 01, 2017 00:35

    Happened to me in 2017.1.0b7
    Second time it happened, don't know the reason for it.

  2. nuthman

    May 22, 2017 20:19

    Just happened to me: 2017.1.0b5

  3. FlopCoat

    May 19, 2017 10:07

    Still around in 2017.1.0b5

  4. tdvance

    May 12, 2017 15:52

    Wait, why is this marked resolved? it clearly isn't....

  5. tdvance

    May 12, 2017 15:52

    Happens in Unity 2017.1.0b4 almost every session.

  6. haskins

    May 01, 2017 22:48

    It's happened a few times to me using Unity 2017.1.0b2.

  7. SpookyCat

    Apr 26, 2017 14:37

    Still happens in Unity 2017b1

  8. GameEverything

    Apr 23, 2017 10:43

    Occurs in 5.6.0b3. I'm just glad that it saves or whatever because I know I sure as hell forgot to save after five hours of work, lol.

  9. swerly

    Apr 04, 2017 18:48

    Continuously happening to me on 5.5.0f3. I don't even have the program open for that long, sometimes <30min

  10. codingcat1

    Mar 31, 2017 00:10

    This happened to me in version 5.5.2f1. Unity left open for at least a day or two without closing (computer on sleep overnight). Received this message after 8ish hours of use on the last day).

Add comment

Log in to post comment

All about bugs

View bugs we have successfully reproduced, and vote for the bugs you want to see fixed most urgently.