Since Tuesday's patch, the Songs "Ballad of the Witch" and "Ballad of the Hero" are both causing Tailwind Mambo to cancel and revert "Con Elemento" to its base state.
This does not happen when using either ballad alongside, "Steel March" and "Blaze Flamenco" and happily work at the same time, so I'm guessing this is not how it is intended to be.
I'm pretty sure that most Bards rely on Tailwind Mambo more than the other two songs that affect "Con Elemento" and The Ballads are both incredibly useful additions to the Bard's DPS, so this could do with repairing.
I've tested this on two Bard characters as that;s all I have, but the same is happening on both.
As far as I can tell, this is happening all the time.