Scalability issue with fft_qsp

[KetpuntoG]

Hi team, I was taking a look at the state of the art for angle calculation in QSP. In particular I was interested in the implementation through fft_qsp.py. I am seeing that in the tests, it is tested up to degree 10. I have tried to set values a little higher like 20 and it stops giving the desired values. I was wondering if this could be due to a bug in the code or on the contrary it is a limitation of the method you may be aware of.
Thanks in advance!