Kenwood DDX5901HD has problem playing Hi-Rez files.

A while back I donated my Kenwood 5901 to a buddy and he has been happily playing MP3's on it via a USB thumb drive with no problem. Recently he ventured into large FLAC files, some of which are 24-bit, 96KHz and the playback is very strange. It is as if someone reduced the speed of playback to 1/3 or 1/2 speed...and playback continues slowly until the file ends or a new lower bit rate or 8-48 kHz file is selected.

When I used this 5901 I either played small FLAC files or MP'3's and did not notice this problem that I remember.

Anyone have any idea what is going on here?

Thanks for any replies.