It has been a painful/tedious experience adding sound effects using third party tools. Any plans to bring back this feature?
It's not something that we are planning to revisit in the near future but it hasn't been said that it's something that we would never attempt to implement again. I can't be any more specific than that.
I agree with Kishore (and others) that this is a crucial element that clients really like. It requires a bit of expertise with a third party audio software element, and lots of searching (often at a cost) to find the right sound effects from additional vendors. Is it the third audio file that breaks the videos? Please see what you can do to add it to a future implementation.