Unity Upgrade Prefab Issue - Null References - Corrupt Cache?

Hi Unity Support,

So I upgraded from 2019.4.22f1 last month to 2019.4.23f1 and hit an issue with regards to field values being nulled on prefabs in the editor.

After reporting the bug (via the official channel - case 1324368 - and this forum) and waiting for acknowledgement of the issue (and hopefully a fix in 2019.4.24f1) none was forthcoming.

I originally reported the issue here...

https://forum.unity.com/threads/unity-update-broke-game.1081598/

And can see that others have also reported it...

https://forum.unity.com/threads/uni...renceexception-argumentnullexception.1089346/

I'm sure there are more and there are some potential candidates here...

https://forum.unity.com/threads/instantiated-prefab-missing-attributes.1041862/

https://forum.unity.com/threads/prefabs-broken-after-2019-3-upgrade.818706/

But three weeks later there is zero progression, not even an acknowledgment.

The 'resolution' was to re-import all, but the import dialog itself states if you need to-do this it's likely the result of a Unity bug and should be reported.

I just made a second attempt to upgrade from 22f1 to 24f1 and hit the same issue. I ran the re-import which works around the issue, however, GitHib reports unexpected deltas. It seems the re-import process has modified a large number of anim, controller, asset, guiskin & prefabs files in one particular third party package that is installed.

The main bug aside, why is Unity feeling the need to modify source files during a reimport? Surely it should just be importing them to the library\cache dependant on the current platform selected.

I would say this is a pretty serious issue, especially as it seems to have worked its way into the 2018 LTS build as well as 2020 & 2021. Going by the one of those posts, it might be a regression.

Could someone at-least acknowledge this please and report any progress? I would have expected more from an LTS build but that's two in a row that I'm skipping as my confidence in using it for a release build is very low at the moment.

 

Just seen this...

https://forum.unity.com/threads/addressing-issues-with-missing-references.890923/

FWIW the projects affected are using Asset Pipeline V2

 

They mostly (or entirely) seem to be references to other components on the same object or in the same scene.

Not all references appear to be nulled, but a lot are. I couldn't spot a pattern (e.g. it nulled references to some of my own components as well as Unity's) but I will happily re-run the process and do a little more investigation if it helps.

 

FWIW

I am seeing more and more posts describing pretty much the same issue now.

Another for the collection...

https://forum.unity.com/threads/a-m...-3f1-to-2020-3-1f1-lts-or-2021-1-0f1.1090936/

 

Hi Steen, any updates please?

I see more people reported the issue over the weekend.

https://forum.unity.com/threads/prefabs-broken-after-2019-3-upgrade.818706/page-2#post-7050823

 

Mine says there's an error while saving the prefab, lists the prefab file directory, and says 'You are trying to save a Prefab with a missing script. This is not allowed.'