Hi,
Surprised no one has reported this (or at least I can't find anything related), but there's a long-standing bug with playing flack sounds that makes the flac playing support virtually useless.
Depending on the compression used, pb plays flac sounds with a chunk of audio missing from the start of audio.
My tests with a 44100, 16 bit, stereo flac sound with different compression rates yielded:
With compression of 3-8, my sound loses about 70 ms from the start, and with compression of 0-2, about 20 ms.
The cutting of the start of audio happens both on Windows and MacOS, with the exception of certain compression rates causing MacOS to throw an invalid memory error.
The sounds play fine in other things, and SoundLength() does report the correct length.
Here's a zip file with the source code, and 9 flac sounds, each saved with the compression rate specified in the filename (0-8).
http://nsstudiosweb.com/test.zip