Code to reproduce the problem:

sys = ctrl.zpk([], [1j], 1)

plt.figure(figsize=(8, 6))
ctrl.root_locus(sys, color='red') #<-- Problem is here

plt.xlabel('Real Axis (σ)')
plt.ylabel('Imaginary Axis (jω)')
plt.grid(True)
plt.show()

In the diagram, you can see the pole is placed at the wrong location. but I looked into it and found a quick solution (though I am not familiar with the code, and it might be deeper than I found)

in the files xferfcn.py (lines 1068, and 1072) there are two arrays that are created of type float, that could later assigned to complex numbers if the input is of type complex. the fix is to just change the type of the array to complex

Then another issue arises in plocus.py (line 267), if the coefficients are complex, it is again casted into a float. I am not sure what this value is used for, but I believe this can be fixed by casting the input type to complex if it isn't already, then using the magnitude of the complex number instead of casting it, which I believe the abs() function will do for default python complex types.

Should be an easy fix, hope this helps