Sourdough rise

I'm looking to see if anyone has a suggest on what is going wrong when I make sourdough. 

If I make the bread with yeast, it rises perfectly and makes a great looking loaf. However, if I use a sourdough culture, the bread is flat. It has great flavor but it is more dense that it should be. I've included at a photo at the bottom but the angles really don't show the difference in height.

I follow the Ken Forkish hybrid method.

With the SD, I freshen the starter overnight. Then I make the "biga" using SD only - it rises well and looks really healthy.

Then I put all the ingredients together (1000g flour) adding 3g yeast. The first rise is great and looks exactly the same as if I had made it with all yeast. I then shape the dough, but in baskets and leave to rise overnight in the fridge. When I take this out there is very little rise. It comes about half-way up the banneton whereas, if I were doing the all yeast version, it would be at the top. I have also tried with all SD but there is no difference. 

Any idea on what I am doing wrong here? Thanks