Curious if you tried a soft reset by holding the volume knob down until screens go black and reboot. That would be an easier fix to attempt, similar to what Teslas need from time to time.
Apple Lossless should be a file with a .m4a extension. According to the owners manual, that should be fine.
File extension
.mp3;.wma;.asf;.m4a;.m4b;.aac;.flac;.mpg;.mpeg;.avi;.mp4;.m4v;.mov;.wmv;.3gp;.mkv;.ts;.mid.xmf;.mxmf;.rtttl;.rtx;.imy;.ogg;.webm;.wav