iPod Classic (160GB) cannot D/L 24 bit WAV songs, previously playable, after latest iTunes update

After updating to iTunes (12.4.0.119) my iPod 160GB Classic no longer recognizes important 2,116kbps (24bit) WAV song files of mastered personal compositions. Data will not D/L to iPod, though the file names & playlist remain. However these song files continue to play from iTunes on my MBP (mid 2012) (2.9 GHz Intel Core i7) (OSX10.11.5) I restored the iPod twice but the song data did not transfer to the iPod. Any suggestions? Should I try going back to the previous version of iTunes? Is this possible? There was no problem listening to these files from the iPod before the update.