The referenced script (Unknown) on this Behaviour is missing!

I keep getting this error all over, in different scenes with different objects (I assume). It happens out of nowhere.
It only happens the first time you load a scene, weird cause if you load it again the warning doesn't show up.

In Packed Play Mode and it also shows in Player Build. Everything works fine in fast mode.

This errors out of nowhere are getting pretty annoying.

 

There are a couple of potential reasons for this. One is a bug, one is not. The one that is a bug, is that instances of objects loaded as dependencies often lose their type. This is an engine bug, rather than an Addressables bug. It is fixed* in 2019.3.0a12 and the fix is being backported to 2018.4.x and 2019.2.x.

The other instance of it occurring is when you have the same object duplicated into multiple asset bundles as an indirect dependency. Same story as above, but not fixable by upgrading, you need that object to explicitly make it into a bundle. The detect bundle duplicates analysis rule can fix that.

* I'm currently reimporting a copy of our project into that version to verify how fixed is fixed.

EDIT: It is fixed! So, it should be on the next two non-alpha releases, hopefully.