I say yes, persist. There was a thread about this that is eluding me at the moment but my understanding is that this is just a 'quirk'. You don't need to keep the screen open, the villagers will complete the huts eventually. I also believe that when it says the huts are complete as you have said, you still get the population boost!

I'm guessing that what happens is each hut has a percentage built and the totals come to 100%...but that is just a guess.

I hope this helps some!