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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. BoraxKid

    Aug 07, 2017 11:25

    Happens here on Unity 2017.1.0f3 on Windows 8 Entreprise 64 bits.

    The Bug Report window did not show up

  2. hht

    Aug 07, 2017 08:38

    Happens very often in Unity 2017.1.0f3 on macOS Sierra 10.12.6

  3. Cemaprjl

    Aug 07, 2017 03:51

    windows 10, 2017.1.0p1, comes several times in a day

  4. Denki_Gaka

    Aug 05, 2017 01:24

    Occurring multiple times each day in 2017.1.0f3. Never saw before that. However, I am getting much better about saving my scene every time before I run. 8^)

  5. BoaNeo

    Aug 05, 2017 00:44

    Oops, forgot the details: 2017.1.0f3 running on OsX, latest mac book pro... Seem to happen regardless of size and nature of the project I have loaded, and so far it has always happened when pressing play (I only have one instance running).

  6. BoaNeo

    Aug 05, 2017 00:36

    Also seeing this every odd-hour randomly after upgrading to 2017.1

  7. archelyte_vz

    Aug 04, 2017 18:32

    This is happening about 3-4 times a day. This is ridiculous.

  8. RFJ

    Aug 04, 2017 07:48

    Yeah BIG problem for me and my team happens at least 3 times a day

  9. Zakari

    Aug 04, 2017 03:43

    ye, this is a big problem for me.

  10. raxor12

    Aug 04, 2017 03:23

    with Windows 8.1too , I just move to unity 2017.1.0f3 and that is when begun the problem

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