Design topology not obeyed

[agarrubio]

In the colab ipynb https://colab.research.google.com/github/generatebio/chroma/blob/main/notebooks/ChromaDemo.ipynb, I have tried 3 times to create a TIM-barrel (CATH 3.20.20) with different lengths in the range of known TIM-barrels.
None of the 3 times did I get something resembling a TIM-barrel. All three times I got a 4-strand antiparallel beta sheet, surrounded by several helices that do not form a barrel.