i had the same problem and posted a thread in here asking about it. the male was desperately building the nest but it would burst. the female was waiting in the balcony waiting for the nest that was never finished. at last they breed with the tiniest nest I have ever seen and he managed to grow it just bigger and bigger. I have now few dozen fry of that spawn.
I have another pair that have the same problem, for some reason I have this pair at a bucket in the open. There is a huge nest with many eggs, but air seems to burst the bubbles, so I covered the bucket with a plastic rapping (leaving a tiny opening for oxygen) and it worked great.