Missing 180 degree label in 'npaeqd' projection

[664787022]

Description

When I set proj='npaeqd', proplot 0.9.7 does not show all longitude labels, but only far bottom label 0°. This problem does not exists in 0.9.5.post332.

import proplot as pplt
import numpy as np

fig, ax = pplt.subplots(ncols=2, nrows=2, proj='npaeqd', share=False)
ax.format(labels=True, coast=True,
          lonlocator=np.arange(-180,180+30,30))

Steps to reproduce

import proplot as pplt
import numpy as np

fig, ax = pplt.subplots(ncols=2, nrows=2, proj='npaeqd', share=False)
ax.format(labels=True, coast=True,
          lonlocator=np.arange(-180,180+30,30))

Expected behavior:   show longitude labels as in proplot 0.9.5.post332  

---

  By the way, how can I make longitude labels like this as in cartopy？ ( showing far top label 180° compared to picture 2)  

import matplotlib.pyplot as plt
import cartopy.crs as ccrs
import matplotlib.path as mpath
import numpy as np

fig = plt.figure(figsize=[10, 5])
ax1 = fig.add_subplot(1, 2, 1, projection=ccrs.NorthPolarStereo())

leftlon, rightlon, lowerlat, upperlat = (-180,180,0,90)
ax1.set_extent([leftlon, rightlon, lowerlat, upperlat], ccrs.PlateCarree())

# add labels
ax1.gridlines(crs=ccrs.PlateCarree(), draw_labels=True,
              xlocs = np.arange(-180,180+30,30), 
              linewidth=1, color='grey',linestyle='--')

# set the boundary
theta = np.linspace(0, 2*np.pi, 100)
center, radius = [0.5, 0.5], 0.5
verts = np.vstack([np.sin(theta), np.cos(theta)]).T
circle = mpath.Path(verts * radius + center)
ax1.set_boundary(circle, transform=ax1.transAxes)

  Actual behavior: Only showing the far bottom label as in picture 1.

Equivalent steps in matplotlib

import proplot as pplt
import numpy as np

fig, ax = pplt.subplots(ncols=2, nrows=2, proj='npaeqd',share=False)
ax.format(labels=True, coast=True,
          lonlocator=np.arange(-180,180+30,30))

Proplot version

matplotlib 3.4.3 proplot 0.9.7 cartopy 0.20.2