Just an update here - I tried this on my Macbook Pro (M1), in both the stable, and beta and have the same issue. Unsure if it is an issue with a video clip, or audio at this point. I used an audio track provided in rush, and have one about 15 second audio clip from my Iphone.
Video is from DJI Mavic 2 Pro. Total is about 40 seconds long, which is why this is so confusing. I've edited videos upwards of 10 minutes in length without issue in the past.