Colin,
I have not seen you raise this question on the new forum which is to be found by clicking this link
However, the answer to you question is that initially the B2 records music as WAV files, then when it is left on and is idle, it compresses these WAV files into FLAC. You just have not given the unit time to do the conversion.
If you have further issues do join us Brennan Users on the new forum.
Fred