But I didn’t get a logical answer.
Perhaps I asked it in the wrong section of the forum.
Please tell me what to do, as I can’t keep updating the project even within LTS 2020.
Thank you!
Duplication:
I can’t upgrade my big project to the new version 2020.3.1f1 (LTS) or 2021.1.0f1.
The project breaks down because many objects lose references to other objects (prifabs).
Even manually set string variables are lost.
Even prifabs on the stage with manually set external properties break down.
What should I do? This is just a nightmare for me!
I stopped on version 2020.2.3f1.
It is impossible to edit such a large number of errors manually!
Before that, everything worked fine for two years - even when I upgraded the project from 2018 to 2019 and from 2019 to 2020.
Is there a way to upgrade Unity Editor to a new version without these errors?
I will be very grateful for any help!
There are screenshots at the specified link. <<<<<<
It feels like a bug. If you can make a subset of your project (the smallest you can) that reproduces the problem, and create a bug report with that project attached, we would like to take a look.
Thanks for the answer! I’ll try to find the time and create a bug report. Although I’ve never done it before. I thought I had described the problem in sufficient detail. Well, ok.
I understand. If you can attach here a small project, the smallest you can, with just a couple of prefab instances that break when updating (and of course, the prefab in the asset folder), then I will create the bug report for you.
The error is confirmed. I have uploaded UnassignedReferenceExeptions_Clean.unitypackage for you (70 Mb). Create a project in version 2020.2.3f1 and import UnassignedReferenceExeptions_Clean.unitypackage into it. Open Update_2021_UnassignedReferenceExeptions scene and see source prefabs (two first screens with green arrows). Then upgrade the project to version 2020.3.3f1 (or to 2021.1.2f1) and see the result (screens with red arrows).
!!! File !!! —> UnassignedReferenceExeptions_Clean.unitypackage https://ru.files.fm/u/qsajff9st
The link will store the file for 2 months!
Please let me know if something goes wrong or if you fix the bug. Thanks!
2020.2.3f1
The bad result after upgrading to 2020.3.3f1 (or in 2021.1.2f1).
This file UnassignedReferenceExeptions_Clean.unitypackage is a clean result variant and has passed !!! THE SECOND !!! export. That is, I created the first export from the original project UnassignedReferenceExeptions.unitypackage (dirty variant without the word Clean) and imported it into the new project version 2020.2.3f1, cleaned it (removed some classes and excessive code) and then upgraded this project to version 2020.3.3f1 (or to 2021.1.2f1). After that, I saw there what I showed in the screenshots. The links were missing right away - I didn’t even press button “Play”.
But if I create an export already from a clean project (the second export) to UnassignedReferenceExeptions_Clean.unitypackage, then after importing it to a new project and transferring it to 2020.3.3f1 (or to 2021.1.2f1) all links are saved as they were, but if you click “Play” I still get these messages in Console :
So I’m giving you a link from the first export but in the form of a project in version 2020.2.3f1. Just open it in Unity Hub in version 2020.2.3f1 and upgrade it to version 2020.3.3f1 (or to 2021.1.2f1). Then you will see that the links disappeared immediately - everything will be as in the screenshots above.
!! File as Unity Project (FIRST EXPORT .unitypackage from source project and FIRST import into new project in RAR in 2020.2.3f1) !!! —> Unity_Update_Error_2021_UnassignedReferenceExeptions.rar https://drive.google.com/file/d/1hUSV4MKqc4cteIVjvrcTHNlH6ldF54B3/view?usp=sharing
—> 147 Mb (strange, but RAR does not compress the project to the size of 70 Mb )
Please let me know if something goes wrong or if you fix the bug. Thanks!
I can certainly create the first clean UnassignedReferenceExeptions.unitypackage from source project without excessive data, but it will take time.
Project in the archive Unity_Update_Error_2021_UnassignedReferenceExeptions.rar, basically, the same thing.
Just what you wanted.
By the way, if you export this project (Unity_Update_Error_2021_UnassignedReferenceExeptions.rar) in .unitypackage and then import it into a new project version 2020.2.3f1, and then upgrade it to 2020.3.3f1 (or to 2021.1.2f1), then the links will already be in place as it should, but warnings will still appear when you click “Play”.
Hi! You didn’t answer. Did you succeed to create a bug report (could you give me a reference)? Did you downloaded the project? Everything okay? Do you have any questions for me? When will I be able to update my project without such errors? Thanks!
Hi! Cool! Thanks! But I can’t see anything on this link. And I can’t register an account in https://fogbugz.unity3d.com/. But I believe that bug report exists. If the error will be fixed, then please let me know in this forum so that I can try to update the project. Thanks!
I realized it now that that link is internal only. This is the public link:
It shows only the description and not the other details, that are still private to unity. So you are not seeing the screenshots and the link for the unitypackage that I uploaded in our repository.
For the next time, if you submit a bug report yourself via the editor, you will get the public link, exactly as in the example you have brought. And that’s the way it’s suggested to do.
I thought I had described the problem in sufficient detail. Well, ok. 
Thanks!