Given the following code:

import control as con
gol = con.tf(1, [1, 2, 2, 0])
rlist, klist = con.root_locus(gol)

When I click on the root locus trajectory on the plot where it crosses the imaginary axis, the gain is reported to be approx 0.7, but I believe the gain should be 4 at this critical damping location for this transfer function. I have not reviewed the code for root_locus to find the specific issue, but wanted to document the problem if it indeed exists.