Sections of my videos are muted

I keep trying to look for any assistance or explanation, but everything I see is talking about when your videos are muted for copyright claims. That's not what's happening to me. I have put in so much time to edit my videos in the TikTok app, I upload them, and then one or two sections have no audio, and the only audio I'm using is my own. What is happening? How can I fix this?