Bug so about the prefabs that disappear

it also happened in 2018 LTS, isn't that when you guys switched over to Neo prefabs?

so it seems to happen with 100% consistency when you import a project from a previous version of unity and some of the API was removed, like, say, [RPC]

Definitely not user friendly
A good motivator to fix scripts though.

since it's a deeply rooted bug I logged it in 2018LTS, you can trace the root more easily like that
case #1240728

 

Once the scripts are fixed unity does another pass at converting assets.

That's odd so I looked through the project and found this AssetPostProcessor. Could this be the reason for such behavior?

Code (CSharp):

1. using UnityEngine;
2. using UnityEditor;
3. using System.Collections;
4. using System.Collections.Generic;
5.  
6. public class GeneralPostProcessor : AssetPostprocessor {
7.  
8.     void OnPreprocessModel ()
9.     {
10.         ModelImporter importer = assetImporter as ModelImporter;
11.         importer.materialName = ModelImporterMaterialName.BasedOnMaterialName;
12.         importer.materialSearch = ModelImporterMaterialSearch.Everywhere;
13.     }
14. }