After updating from 2017.4 to 2018.3 my prefabs lost their "internal" references

Hello,

I haven't found anything so far regarding this issue, I've updated my project from Unity 2017.4 to 2018.3 and now if one of my prefab script has a reference to one of its component or children I get an "UnassignedReferenceException" while instantiating it.

For example I have a DoubleDoor prefab with 2 child gameobject, DoorLeft and DoorRight, they are properly assigned to the DoubleDoor script in the prefab editor but when I try to instantiate it, I will get the UnassignedReferenceException.

I have found a fix, I need to manually set a tag for all the prefab content, and "Untagged" Tag will not work so I have to go over all my prefabs and ensure they all get properly tagged. Which is quite time consuming.

Does anyone ever encountered something similar? Is there a specific reason for this behaviour? Is there a documented process that I missed to update prefabs in Unity 2018.3?

Thank you in advance for any help you could provide

 

Thanks for your reply

I was not able to reproduce the issue in a new project.
Moreover after reverting my project to 2017.4 a third time and restarting the migration to 2018.3 the issue seems to have dissapeared.

Guess I'll just move on and see if any new issue arise.