In the original Post I said that in versions prior to 2.3.6 that LAV Splitter and decoder worked - this was with wav and dts file extensions.
I can't try this at the moment so I could be wrong (damn work) but I think if you try to play wav or mp3 files in NPVR it will render the files without an audio codec in the filter chain (according to the log) I expect even if the extension is dts the header is still wav and so it tries to play the raw wav content - nasty.
Could it be the NPVRMP3Reader.ax that is actually doing the decoding?
It's not an overly complicated system - it's more - overly simple operatives
I'm pretty sure that npvrmp3reader is not used for wav/dts. you an unregister it to make sure though.