I'll explain the perceived bug and explain why I'm an idiot! Might be a useful reference.
I'm working on a project which is mostly MIDI but wanted to run a sample audio track to follow, which I did. Having built up the MIDI arrangement, I'm now ready to rerecord the original audio track.
All audio is deleted from the audio files folder in the project folder and there are no audio tracks visible in the Main Window but I can still hear my original sample audio track!
Took awhile until I realised I'd tuned the original track with Melodyne and the plug-in was still active in the mixer window, so Melodyne was playing it back!
Just saying in case anyone else strikes this........

Bob