The following script produces an x less than -1:
from UncertainSCI.families import JacobiPolynomials
J = JacobiPolynomials(alpha=1.553,beta=2.270)
u = 4.6808507655704545e-05
x = J.fidistinv(u, 0)
Probably a bug in how the degree-0 fast approximation is constructed.