It's an error on the new 5.1 track. I first noticed it at screening of the restored version. It turns out I even made a convenient mp3 demonstrating this.
The first 12 seconds are the mono track and the remix starts at 14 seconds. Note the music after Michael shouts, "Rocco, alive!"...
While you're at, you could also fix the music after the assassination attempt on Michael in Part II. It's correct on the mono track, but is out of sync on the 5.1.
I watched the first film and Part II this weekend with the original mono audio. Here's why.
WARNING: If wearing headphones this gets a little loud when the remix plays.
From last month...
https://deadline.com/2020/02/the-conversation-francis-ford-coppola-1974-palme-dor-winner-set-for-re-release-with-new-35mm-print-dolby-5-1-remix-1202863193/