This file is broken. On one of the instruments (strings - e.wav), "carry" is on. This instrument only ever plays once on each channel, so you just get one chord.

Well, then turn it off!

Seems that xmplay and xmp both reset the envelope and retrigger the note when it hits the note off, I don't get why but I'll try to investigate that later. For the time being I checked in a patch to make the envelope reset when a note is triggered and there's nothing playing, which I'm not sure how I managed to not ever notice before since it only makes total sense that you'd want new notes to start with the envelope not at the end :P