Adding Angles in Multicam

Question summary
If I have 3 clips with TC and create a Multicam clip that is correctly synced, how can I then add an extra clip without TC and have it sync via audio?

My attempts
I Right clic on a clip and select Add Angle, then drag the extra clip into it. Now it is clearly not synced. I tried Sync to Monitoring Angle, but there is no selection to use audio and I don't understand this step.
HELP PLEASE

Actual setup
We shot an event with 5 cameras all had scratch sound:
1) Canon XF605 with time code, which appears not to have jammed correctly (bummer!)
2) Canon X40 using Tentacle Sync E
3) Sony A7s3 with Tentacle Sync E
4) Sony NX5R no TC
5) Fuji X-T4 internal TC not jammed

Additionally I had a stereo feed from the PA desk going to a MixPre 6ii which had TC jam synced to the Tentacles. It was also feeding audio out into the Canon XF605.
I ran Tentacle Sync Studio on #2 and #3 and synced them to the MixPre sound files using TC. 
I can't figure how I can now add the other 3 cameras to the Multiclip, using audio to sync with.

From support.apple.com/guide/final-cut-pro/sy...gles-ver23c76b1a/mac

Sync Angle to Monitoring Angle: This option compares the audio waveforms in the selected angle to the waveforms in the monitoring angle, and then moves the clips in the selected angle to sync them with those in the monitoring angle.