So to summarise I changed:
“Project/Corona/Resource/Sounds/keypads” to “Project/Corona/Resource/Sounds/Keypads” but after running the build script “Project/android/assets/Resource/Sounds/keypads” remained lower case. I deleted the whole “assets” folder, ran the script again and it was OK after that.
As I mentioned though I also noticed files I had moved previously, had not had their old locations deleted. So for example I had something like:
Project/Corona/Resource/Sounds/myWavFile.wav
Then moved it to:
Project/Corona/Resource/Sounds/Keypads/myWavFile.wav
In assets, the file appeared in both those locations which is why I mentioned that it obviously doesn’t strip out its contents before copying new stuff in.