I have a sound source on my test map, which happens to be empty (no idea why it's there, probably an error from my part):
I made a few changes to my sound catalogs, so I pressed autodetect. And I noticed a sound entry adding itself.
This is what you can see if you press "Deselect all" first, then "From sound sources":
After testing, I found it was because of this empty sound source.
I have not tried rebuilding the level this way, I just removed the sound source and carried on.
I have a sound source on my test map, which happens to be empty (no idea why it's there, probably an error from my part):
I made a few changes to my sound catalogs, so I pressed autodetect. And I noticed a sound entry adding itself.
This is what you can see if you press "Deselect all" first, then "From sound sources":
After testing, I found it was because of this empty sound source.
I have not tried rebuilding the level this way, I just removed the sound source and carried on.