fitfrail possible bug

[TFCox]

I am using fitfrail for the first time. I have a dataset where the following error appears:
Error in nleqslv(init.gamma, fit_fn, control = list(xtol = control$reltol, :
initial value of fn function contains non-finite values (starting at index=1)
Check initial x and/or correctness of function
(Similarly if I use log-likelihood)

But if I use a small subset of the data - it works! N=603 for full dataset.

Thanks