I'll have a look, probably wrong DMACON wait. Next time you can create a bug on mantis.whdload.de (no need for this time)
I made a change can you test?
FantasticDizzyAGA.zip
(I have aggressive WinUAE settings to detect faulty music and didn't hear anything unusual here but it's sure that game doesn't wait after dma has been written to stop sound so...)