I didn't seem to have this problem the last time I worked on a multi-cam project. When I'm working with a clip, and play from the timeline, the view will switch to one up view while the clip is playing and then back to 2-up when I pause. And then sometimes it play two up all the time as I would want it to after screwing around with it. I'm not sure exactly how to control this and what I'm doing to cause either.
I have multi-clip playback checked and "open" playhead sync.
I have had this problem before too. This only happened when the footage was rendered. See if that is the problem. If so, just click on the flim stip icon to the left of the track to hide it. Then click it again and your render files should be gone. Hope that helps.