I have just discovered a similar problem. When I try to play a FLAC file (24/96) it crashes the whole Pi requiring a hard restart to get it working again. I also have a Hifiberry dac+pro. A 16/44 file plays with no problem. In the past I have been able to play the 24/96 files, but I have made many updates since I first played them and only stumbled on this problem yesterday.