In the online manual:
https://help.magix-hub.com/video/vegas/22/en/content/topics/7-edit/synchronizing_video_in_multicamera_projects.htm

Under the section titled: "Synchronizing Multicamera Audio"

It says:

new since VEGAS Pro 22
"Synchronizing multicam events based on the audio from the clips the events hold has been completely reworked. You can now select multiple events and quickly synchronize them with options optimized for the type of audio contained in the clips.

To synchronize files based on the audio (and they can be audio-only files, video files with audio, or a mix) first add each file to separate tracks so each now sits on a different track than each of the others. Of course, for synchronization to work, the files must have been recorded simultaneously so that they contain exactly the same source audio. It’s best if none of the files starts at the very beginning of the timeline.

The synchronization process will move timeline clip events as necessary to line the audio of each file and any of the events may need to move earlier or later on the timeline. If one of your events needs to move toward the start of the timeline, but it’s already sitting at the very beginning, the synchronization will fail since the event can’t move any further to the left. Give yourself some space between the start of the project and the start of the events on your timeline.

Click the audio event that you consider to be the “target” event, that is, the event you want to match the others to. This event will not move, and each of the other events will move to accomplish the synchronization. Now, hold the Ctrl key while you click on each other audio event that you want to synchronize. As you see in the image above, each of the audio events has been selected (indicated by the yellow highlight) while their grouped video events have not been (indicated by the blue highlight).

Now choose Tools | Multicamera. Depending upon the audio material in your files, select the most appropriate of the synchronization options at the top of the cascading menu. For instance, my file contains both speaking and music, so I choose the Synchronize Mixed Audio to Align Events. VEGAS Pro analyzes your audio files and moves repositions the events as needed to synchronize them. If the first synchronization type you use doesn’t give you results that you’re happy with, undo the edit and try a different type."

I'm using v22, and coincidentally, the same type of footage as given in the manual's example (music and voice). I don't see the "Synchronize Mixed Audio to Align Events" anywhere (is the manual wrong?) I only see Synchronize Audio to Align Events. Also, when I try this feature, 1) it takes forever on a 25 minute clip, and 2) the audio didn't align correctly after it was finally finished. What am I missing here?

My main camera with the good audio is a stereo track, and the second camera is the reference audio for syncing, also stereo, but same audio on both channels.