I am trying to plot step response of a 3rd order process Gp, controlled with a P controller.
Gp = 6/[(s+1)(s+2)(s+3)]
I am using v0.8.3

from control.matlab import *

Gp = tf(6,[1,6,11,6])
Gc = 10
Gor = Gp*Gc/(1 + Gp*Gc)
y,t = step(Gor)
# Plotting code

Gor has 3 poles at (-6, sqrt(11) j, - sqrt(11) j ) and the expected behavior is sinusoidal oscillations after the initial transients have died down (ie t > ~ 2/3)
But what I get is an unstable system:

Octave gives the correct result (ymin 0.113, ymax 1.705 after transients):