Apple Lossless plays on Touch and iPeng9 but not SB Classic? (LMS 7.9.1)

Happy Holidays!

Just upgraded from my trusty ReadyNAS Pro6 to a new ReadyNAS 524x.
Everything went smoothly, but I just noticed ALAC (MP4) files that play perfectly through the SB Touch and the iPhone 6SE (via iPeng 9) will not play on the Classic.
Error on the Classic reads "Problem: Can't Open File For"

Details:
Squeezebox Touch (firmware 7.8.0-r16754)
Squeezebox Classic (firmware 137)
LMS 7.9.1

Is this a known issue? Apologies in advance if I missed the thread.
Any direction or assistance would be most welcome.

Thanks!
-Alan