Can't read certain type of audio files

[Peter@57m]

I had my tracks saved as WAV and tagged using MediaMonkey. When I started using MinimServer, it was like you, to use it with Lumin. However Lumin does not read the tags on WAV files, so you don't see them.
If you use Kinsky you will see them, but depending how they have been tagged, some may not be as you expect them. I didn't have this issue with Twonky which I had been using.
So I decided to transfer all my WAV files to Flac, you can do this with MediaMonkey and I'm sure with many other programs.
I then cleaned up a few remaining tags which were not being read correctly.
I use the Wav24 option in MinimServer as I feel WAV arriving at my DS sounds better than Flac.
I have not come across any downside from doing changing the format, in fact many programs have better support for flac.
I am very pleased with MininServer and really like Lumin. I occasionally use Kinsky for stored playlists and for some custom tags. But Lumin is due to add some form of custom tag support so it will then be just playlists.
I suggest you keep using Lumin with the files that are there for a while to make sure it's the control point you want to use. If so, go ahead and convert the files.