A large amount of my music collection is ripped from my CDs as WMA Lossless. It seems that Plexamp (or mpd) is failing on a significant number of my tracks. Note that they play through the Plex server web app.
An example file that failed through PlexAmp, but played through the Plexamp has the following metadata from the Web client:
Media Info from Windows Media Player:
wma player info:
929 Kbps
Windows Media Audio 9.2 Lossless
VBR Quality 100, 44 kHz, 2 channel 16 bit 1-pass VBR
Media Info from Plex Web App:
Files
07 Angie.wma
Media
Duration 4:31
Bitrate 877 kbps
Container ASF
Part
Duration 4:31
File 07 Angie.wma
Size 28.43 MB
Container ASF
Codec WMALOSSLESS
Channels Stereo
Bitrate 1152 kbps
Album Gain -3.44
Album Peak 336460390220045549992026835293933928448.000000
Album Range 9.581674
Audio Channel Layout stereo
Gain -0.46
Loudness -17.54
Lra 8.21
Peak 0.998901
Sampling Rate 44100 Hz
Stream Identifier 1
Codec LRC
Format LRC
Timed Yes
Codec TXT
Format TXT
The analyzer seems to also have problems too… sometimes able to calculate a waveform and sometime not.
Screencap of it analyzing but not playing audio… (also the analysis is a bit suspicious)

Windows 10, 10.0.16299.0