Here's an option to remove in the background music tab.

If you "Edit" the video, you can find this panel on the left. If you're on the screen to select a video, you can remove all the background music from the dropdown at the top.

A quick tip: to avoid copyright infringement. it could be due to a preset you created with that music. Just delete or create a new preset in that case. Here's a video on presets: https://www.youtube.com/watch?v=YEPAOQkyvfs&t=2s