No audio in sequence, while audio present in source monitor

I have footage from both a GoPro Hero 11 (.mp4) and an iPhone 15 (.mov). I imported them in a brand new project, on my hard drive, not an external drive. If I play them in the source monitor, I have sound. I set in/out and drag that segment into a sequence, and sound is still there. If I set in/out on a different part of the same file and drag it into the same sequence, there's no sound with that. No audio track for the new bit. The audio track for the first segment is still there.

This is not something I've encountered before - I've been doing this kind of workflow without issues before.

I've done some searching and the solutions I've seen is to delete the sequence and start a new one. Which is working as long as I don't try to add new footage to an existing sequence.

There's got to be a fix for this, otherwise it makes Premiere Pro utterly unusable.

Any suggestions would be very much appreciated.

Premire Pro 24.6.1

MacOS Sequoia 15.0