Certain fov fail to image

[epaell]

I've been trying to use hipspy to generate a series of frames for an animation (where I pan and zoom across a HiPS image) but have been running into an issue where certain fields-of-view result in the following error:

./test1.py Fetching tiles: 100%|██████████████████████████████████████████████████████████████████████████████████████████| 142/142 [00:07<00:00, 17.83it/s] Traceback (most recent call last): File "./test1.py", line 15, in <module> result = make_sky_image(geometry, hips_survey, 'png', precise=True) File "/Users/len067/miniconda3/lib/python3.8/site-packages/hips/draw/ui.py", line 46, in make_sky_image painter.run() File "/Users/len067/miniconda3/lib/python3.8/site-packages/hips/draw/paint.py", line 148, in run self.make_tile_list() File "/Users/len067/miniconda3/lib/python3.8/site-packages/hips/draw/paint.py", line 178, in make_tile_list self.draw_tiles = [tile for children in tiles for tile in children] File "/Users/len067/miniconda3/lib/python3.8/site-packages/hips/draw/paint.py", line 178, in <listcomp> self.draw_tiles = [tile for children in tiles for tile in children] TypeError: 'HipsTile' object is not iterable

An minimal version of this script is:
`
#!/usr/bin/env python
from astropy.coordinates import SkyCoord
from astropy.coordinates import Angle
from astropy import units as au
from hips import WCSGeometry
from hips import HipsSurveyProperties
from hips import make_sky_image

coord = SkyCoord(Angle(303.74380308, unit=au.deg), Angle(-56.25561379, unit=au.deg), frame='fk5')
hips_survey = HipsSurveyProperties.fetch('https://www.atnf.csiro.au/research/RACS/RACS_I1/properties')
geometry = WCSGeometry.create(skydir=coord, width=3840, height=2160, fov="3.2666666666666666 deg", coordsys='icrs', projection='SIN')
result = make_sky_image(geometry, hips_survey, 'png', precise=True)
`

It almost appears as something happens when shifting from one HiPS level to another because I can image a sequence of fovs fine (e.g. fov="3.2 deg" works fine) and then a number will fail, then it'll start working again, then as the fov gets large the same thing will happen again (I ran these in parallel so now I have various gaps in my animation which I just can't seem to generate).