multicam editing: sometimes can't switch angle?

I have a multicam track that has 2 video plus 3 audio tracks. It is an interview and the 3 audio tracks are mics for the three people in the interview. The audio that links with the video are not used; other than for sync purpose.

So what I have is
angle 1: HD camcorder #1
angle 2: 4K camcorder #2
angle 3: lav mic 1
angle 4: lav mic 2
angle 5: lav mic 3

While choosing the angle, sometimes merely clicking on the angle in in the left monitor switches the angle. Sometimes I have to alt-click, and sometimes neither click would switch the angle. Pressing the numeric keys also doesn't do anything. I'm trying to switch audio from angle 3 to 4.

I'm a newbie and this is the first time I use this feature. What is the most likely mistake I'm making?

davinci multi.jpg (358.67 KiB) Viewed 457 times

free version 15.1.1.005
windows 8.1
i7-4790k
32GB ram
Nvidia GeForce GTX 650

I've found that multicam in Resolve works best when you include only video clips (with or without audio). Manually sync the audio only clips underneath the multicam clip in the timeline.