Potential bug when changing `planet.lam` parameter?

[catrionamurray]

Hello! I'm having an issue when I change the planet.lam parameter where the spot seems to move strangely w.r.t both the stellar pole and planet transit chord. E.g. setting up the system as follows:

from batman import TransitParams
import astropy.units as u
from fleck import Star

planet = TransitParams()
planet.per = 88
planet.a = float((0.4*u.AU / u.R_sun).decompose())
planet.rp = 0.1
planet.w = 90
planet.ecc = 0
planet.inc = 90
planet.t0 = 0
planet.limb_dark = 'quadratic'
planet.u = [0,0]
planet.lam = 0

inc_stellar = 90 * u.deg
spot_radii = np.array([[0.2]]) 
spot_lats = np.array([[50]]) * u.deg
spot_lons = np.array([[0]]) * u.deg

times = np.linspace(-0.5,0.5, 100)

star = Star(spot_contrast=0.5, u_ld=planet.u, rotation_period=100, )
lc = star.light_curve(spot_lons, spot_lats, spot_radii,
                      inc_stellar, planet=planet, times=times)

produces as expected:

But if I change only planet.lam=30 I get the following:

It seems like the spot has moved in the opposite direction to the stellar pole? If I change planet.lam=90 the problem persists: