Hi @stuartbeattie 
Welcome to Waves forum.
Basically, Tune scans only when it recognizes audio content, meaning that real empty sections in the audio file are not scanned.
To avoid confusion, we suggest scanning an entire vocal channel before editing in Tune as it may raise confusion when scanning a section of a song, working on corrections, and then scanning new sections. (Tune automatically switches into Scan mode when playing un-scanned regions)
It would also be good to “chop” the vocal so there are audio religions only when the singer actually sings.
@simon.a.billington - Thanks for the feedback You’re welcome to share your feature requests here.