Question Why do my bundles have Missing(Object) in the preload table?

This may be entirely an issue with the Asset Bundle browser, which was a tool that was created prior to Addressables and which unfortunately cannot handle AssetBundles with a lot of objects (because it tries to populate the UI with too many entries).

Normally it should not be necessary to inspect things at the preload table level. This is some internal book keeping required by Unity. It tracks all the objects that will be loaded in conjunction with loading each root object (e.g. the material, prefab etc etc). Those objects can actually be "built-in" shaders and other objects, or objects inside other AssetBundles.

I suspect that the UI is trying to resolve the references back to objects in a way that doesn't work for all object types, perhaps built-in objects show up as Missing? So unless you are observing that something is actually broken i suspect this is more of a UI limitation than actual missing data.

If you feel like digging in to understand a bit more about how things work then it is possible to look at the raw info of the references by expanding the AssetBundle with UnityDataTools (or WebExtract / Binary2Text), that would show exactly what those "Missing objects" entries point to.

As an example small Preload table:

Code (CSharp):

1.   m_PreloadTable  (vector)
2.         size 2 (int)
3.         data  (PPtr<Object>)
4.             m_FileID 1 (int)
5.             m_PathID 8028051458226250111 (SInt64)
6.         data  (PPtr<Object>)
7.             m_FileID 0 (int)
8.             m_PathID 7395359030061443441 (SInt64)
9.  

The first object has m_FileID > 0, so that means it is inside another file. There is a listing of the external files at the of the file. If the filename has a name like "CAB-..." then it is inside another AssetBundle.

The second object in the example above is inside the same AssetBundle file, e.g. the ID 7395359030061443441 will be found assigned to an object directly in that same UnityDataTools/binary2text dump.