I've bought a DSD64 album from HDTracks and the tracks plays perfectly on my PC using Tascam Hi-RES Editor.
Also plays fine via USB on my Naim ND5XS.
It streams nicely from QNAP/Asset until the last second and I get a loud crack; it them moves onto the next track, clicks at the end and so on. Asset is configured to play DSF files "as is".

Any ideas? Have I missed something?