iMovie closes when using voiceover

I use my iPhone 8plus to make and edit videos. I have tried at least ten times to add a voiceover on my video, but after about two minutes, the app closes out. Every time. It hasn’t done this before and I’ve spent a long time editing previous videos. I checked to see if it needed an update but it doesn’t. I tried turning my phone off and then on. And I made sure nothing else was running in the background. Is there anything I can do to fix it? It’s the finishing touch for my video and I can’t refilm it. Does voiceover have a time limit?