Ok, more testing has been done and it appears that gapless playback is not working correctly when playing normal files. There is a gap between tracks when playing music files (no cue file involved). I have attached sample files, mp3 and FLAC for testing and a recorded sample of the error. The error can be heard at the 17 second mark.
I have tested using Foobar player and these files work correctly.
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But we can hear a tick when consecutive files are not on the same number of channel and not the same samplerate if i'm not wrong.
So if all files are the same gapless will work correctly but files to files with different samplerate / channel, a new mixer will be involved.
These test files are all the same and should play correctly. They are also from a mixed CD and should continue from track to track with no gap, as they do in Foobar.