I start in both, decide it's not working and switch to a single POV. I then start again, write and decide the same. I change to the other POV, write again and come to a halt with the same conclusion. Eventually I decide that writing from both was the way to go after all and whilst rolling my eyes, I sigh loudly and put them back together again.
I have been frustrated with myself wasting so much time head hopping. I mean, I wasn't writing a chapter each time, it was getting on for 30.000 words. But then I realised: I am not a big plotter, I tend to get an idea, scribble out a rough plot and then head into it. Plotters spend time getting the feel of each character, fleshing out their wants, needs and fears etc before they get started. I learn about my characters as I go along. Maybe this is just my way of getting to know each of them better. When I bring the two PsOV back together again, I have a much better understanding of what makes each of them tick.
So I've stopped beating myself up about it and put it down to research. Am I changing into a kind of plotter? Perhaps I am.
Onwards, now. I have researched enough.