If you search in the c++ source for parts of the message you will find it in \Source\Runtime\CoreUObject\Private\Serialization\AsyncLoading.cpp in the function FAsyncPackage::PostLoadDeferredObjects.
The array ObjLoadedInPostLoad contains all the objects and can be inspected in debugger. I don’t know what Lyra wants, but in our project it seems to be a lot of blueprint internal stuff, like events and functions, components, etc. Things we do not have control over at all.
I tried to cook and run DebugGame. Got none of the errors. But the code does not seem to run at all outside editor(?). At least no breakpoint could be set now. Maybe this means it can only happen in editor.