Muted tracks in multitrack with effects are still being "processed" in mixdown

Hi,

I'm hoping someone can explain this odd behaviour to me - basically when exporting a multitrack mixdown, if I have any muted tracks with effects assigned, the export time is, let's say 10mins for example. If I remove the effects of the muted tracks the export time is reduced to a couple of minutes. So Audition is still processing the effects on the muted tracks in the export! Why? Surely, Audition should 'see' that the tracks are muted, thus not required in the final mixdown, so ignore them...?

Thanks.