Echo on audio after export
I had a problem with an artificial echo created after exporting a video with an Essential Sound effect on the audio. Its a Multicam edit with 2 cameras and 2 separate audio sources each on a separate talking head. I applied Essential Sound effects on the audio and I made sure both sources of audio was perfectly synced so there was no echo and sounded great on the timeline. However after exporting the video there was an echo created that wasn't there before. The final solution I discovered was to have that sequence nested and then apply the effects then export.
I don't know if that is expected but it sure seemed like a bug to me if it was only an issue after exporting it.

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Jason Joelson commented
I had the same problem but what I did is made a new blank sequence copied the other sequence and pasted it in the new timeline and it worked.