Inconsistent results between 2.2.1and 2.3.1

[fmaussion]

Code Sample, a copy-pastable example if possible

import pyproj
print(pyproj.__version__)

srs = '+ellps=WGS84 +proj=ob_tran +o_proj=latlon +to_meter=0.0174532925199433 +o_lon_p=0.0 +o_lat_p=80.5 +lon_0=357.5 +no_defs'

p1 = pyproj.Proj(srs)
p2 = pyproj.Proj('+init=EPSG:4326')

print(pyproj.transform(p1, p2, -20, -9))

Problem description

The result of the above transformation is correct in 2.2.1, and completely off in 2.3.1:

2.2.1
(-22.243473889042903, -0.06328365194179102)

and

2.3.1
(107.25283559403462, -27.893778994303773)

Expected Output

Same results in both versions.

[snowman2]

Likely related: OSGeo/PROJ#1525

[snowman2]

This matches the output of PROJ. I would raise this issue here: https://github.com/OSGeo/PROJ

$ echo "-20 -9" | cs2cs -f '%.2f' '+proj=ob_tran +o_proj=latlon +ellps=WGS84 +to_meter=0.0174532925199433 +o_lon_p=0.0 +o_lat_p=80.5 +lon_0=357.5 +no_defs' '+init=epsg:4326'
107.25	-27.89 0.00