Can't access host object member using DISPID_VALUE (DISPID == 0)

Description
Member not found error when accessing any properties or methods from a COM object, even though others work fine.

Error message:
Uncaught Error: Member not found. (0x80020003)
at RemoteMessenger.postSyncRequestMessage (<anonymous>:1:10533)
at Function.getHostProperty (<anonymous>:1:23331)
at Function._getAmbiguous (<anonymous>:1:13956)
at Object.get (<anonymous>:1:15574)
at <anonymous>:1:3

Code:

// throws error
chrome.webview.hostObjects.sync.unity.ShellSecurity.Stream.UserID

// also throws error
var s = chrome.webview.hostObjects.sync.unity.ShellSecurity.Stream;
s.UserID

There are numerous other objects, methods, properties off the unity object that all work fine. There is nothing special about the object's IDL, or the C++ class that implements it. It uses the same IDispatch implementation as all of the other objects.

When I debug the C++ code for the object it is not calling GetIDsOfNames, but instead calls Invoke with a DISPID of zero and a parameter of "UserID". The other objects that work fine first call GetIDsOfNames and then invoke with the returned DISPID.

Version
SDK: 1.0.818.41
Runtime: 95.0.1020.44
Framework: WPF
OS: Win10 20H2 19042.1348

Repro Steps

Screenshots

Additional context
IDL Excerpt:

[uuid(...), oleautomation, dual]
interface ISecurity : IDispatch
{
  [id(1), helpstring("method Deserialize")]
  HRESULT Deserialize([in] BSTR EncodedString);

  [id(2), propget, helpstring("property UserID")]
  HRESULT UserID([out, retval] long * UserID);

  ...
}

AB#37256935