why does scipy.integrate.quad fail for some interval of this integral

To reproduce:

# use scipy to create random number for f(x) = 2x when x in [0,1] and 0, otherwise
from scipy.stats import rv_continuous
class custom_rv(rv_continuous):
    "custom distribution"
    def _pdf(self, x):
        if x >= 0.0 and x <=1.0:
            return 2*x
        else:
            return 0.0
rv = custom_rv(name='2x')
from scipy.integrate import quad
print(quad(rv._pdf, -10.0, 10.0))
print(quad(rv._pdf, -5.0, 5.0))
print(quad(rv._pdf, -np.inf, np.inf))

Output:

(0.0, 0.0) # for [-10,10]
(1.0, 1.1102230246251565e-15) # for [-5,5]
(1.0, 2.5284034865791227e-09) # for [-inf,inf]

Context:

I'm trying to create a random variable with a custom p.d.f: f(x) = 2*x if x is in [0,1], otherwise f(x) = 0.

This random variable didn't work and I tried to debug by checking the integral of p.d.f using quad.

What I found was that the integral was not consistent. For some intervals like (-inf,inf) and (-5,5), it's 1. However, for intervals like (-10,10), it's evaluated to be zero, which is quite unexpected.

Any idea what went wrong here?

Thanks!