Here is what I've learned:
Files that aren't recognized correctly (VR format), but do appear in the Skybox network file browser via Windows 10 DLNA server can be made to play correctly simply by manually selecting the appropriate VR format. If I remember right filename VR format identification is not supported over DLNA anyway, only local files have the format identified from the filename, so this may not be an issue for Skybox to troubleshoot but rather a future enhancement which you guys are already aware. Again, correct me if I'm wrong.
The main issue that I'm not sure is related to Skybox is failure to list VR MP4 files in the Skybox network browser that are part of Windows 10 DLNA video library. I also tried browsing the network files available from the DLNA server using VLC for Android with the same results. There is some indication that moving files to a new folder and adding it to the library (on the Windows DLNA server) prompts a re-scan that changes which files are seen by Skybox/VLC. But it seems unreliable. So probably this is where the problem lies. But it seems to have little to do with the individual files, as sometimes a file will be listed in the DLNA video library, and sometimes it won't, depending on what happens when I move the files to a new folder and re-add to the library.
I apologize for my slow response. I'll gladly make files available if you think it will help, but the DLNA library visibility issue doesn't seem to be related to the files themselves. How would you suggest proceeding to troubleshoot this issue? It does seem as though it might be an interaction between Android DLNA client and Windows DLNA server? Or maybe Windows DLNA server doesn't refresh? I will try viewing the DLNA library on a Windows laptop to try and narrow down the problem to the server, or the Android DLNA client(s).