Unusual Problem with iMovie, GarageBand and YouTube

I created a video for one of my wife's real estate listings - slide show with background music and a voiceover - on my MacBook Pro. I used iMovie for the video and music track. Then, due to a glitch in iMovie, I imported into Garageband for the voiceover. Uploaded to YouTube and it worked fine. Price of property changed and I updated text on two slides, making NO changes to the voiceover. Exported back into GB and then to my Desktop, where it works perfectly. But when I upload it to YouTube, the voiceover doesn't play. After uploading 7 times, the voiceover finally worked, though I have no idea why. I played it 3 times on YouTube to verify it was working and went to bed. The next day, the client listened to it and heard no voiceover, which I confirmed last night. Very strange! I'm trying to figure out how to contact YouTube directly with the issue, but they apparently don't have a LiveHelp Desk and they don't make it easy to reach them. This issue is not covered in their FAQs. Since the video was created on a Mac, I thought perhaps someone here might know how to resolve this issue. Any help is greatly appreciated.