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You may want to try delaying the audio one or two frames (depending on your framerate). Often if things happen exactly on the same frame they don't appear to be aligned. Professional animators will usually skew their audio tracks. You want the visual to be just slightly ahead of the audio, because the audience needs time to take in what's on screen before the sound, but just barely. Try one frame, and if that doesn't work, take it to two.

Good luck, hope it goes well!