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Won't Fix

Fix In Review for 2019.4.X, 2020.3.X, 2021.1.X



Found in





Issue ID




Prefab script field reference is lost when project is upgraded

Asset Import Pipeline


Reproduction steps:
1. Open the project ("") in not reproducible version
2. Open "backgroundEnvironment" prefab
3. Select "airplane_pivot" Game object and open the Inspector window
4. Inspect Airplane GO script field
5. Close the project and open it in a reproducible version
6. Repeat steps 2-4

Expected result: Airplane GO remained the same
Actual result: Airplane GO script field reference is lost

Reproducible with: 2019.4.14f1, 2019.4.24f1, 2020.3.4f1, 2021.1.3f1, 2021.2.0a13
Not reproducible with: 2019.4.13f1
Could not test with: 2018.4.33f1 (script errors)

  1. Response avatar

    Resolution Note (2021.2.X):

    The supplied bug has an asset which we believe has been upgraded from 2019.3 to 2019.4, before being re-opened in 2019.3. At Unity, we don’t officially support the downgrading of assets between versions (though it may work on occasion).

    If you have this issue without bringing assets from later Unity versions, I would suggest filing a bug with your project. We’d be happy to look into it!

Comments (4)

  1. 2614a132ebe47f793f90adc31db9197f?d=mm


    May 10, 2021 09:34

    4 out of 4 projects are having issues when upgrading from 2019.4.21f1 to 2019.4.24f1+.
    None has anything to do with 2019.3 or whatever downgrade.

    The only (partially) workaround so far is deleting the entire Library folder and letting Unity to rebuild it again.

    This "Won't fix" is simply unbelievable, on a bug impacting so many projects since several weeks.
    Again, speechless.

  2. Ddf802dc5c237baf0f9976cd028fd181?d=mm


    May 07, 2021 01:44

    Not fix!!

  3. 0abc5888f09e42c270f67bfaf199e0ad?d=mm


    May 03, 2021 11:18

    Reproducible with 2021.1.5f1 too. Would love to see this fixed.

  4. 47d9e9615b458037bf2f1847802524cc?d=mm


    May 02, 2021 21:21

    This essentially make upgrading impossible for any project. Should be highest priority.

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