Error for KerrGeoOrbit when a=0

[VojtechW]

It seems that the analytical method for KerrGeoOrbit returns expressions that are not manifestly real for $a=0$.

MWE:
orbit = KerrGeoOrbit[0, 20, 0.9, Cos[\[Pi]/8]];
{t, r, \[Theta], \[CurlyPhi]} = orbit["Trajectory"];
Show[ParametricPlot3D[{r[\[Lambda]] Sin[\[Theta][\[Lambda]]] Cos[\ \[CurlyPhi][\[Lambda]]], r[\[Lambda]] Sin[\[Theta][\[Lambda]]] Sin[\[CurlyPhi][\[Lambda]]], r[\[Lambda]] Cos[\[Theta][\[Lambda]]]}, {\[Lambda], 0, 20}, ImageSize -> 700, Boxed -> False, Axes -> False, PlotStyle -> Red, PlotRange -> All], Graphics3D[{Black, Sphere[{0, 0, 0}, 2]}]]

Returns

This appears for any $p,e,x$ at $a=0$.

[nielsw2]

I am not sure why this error appears as the trajectory evaluates just fine and the plot also works. The error message only appears with ParametricPlot3D, and does not appear if you instead use a Table.