contourf missing levels

[pgoddard08]

Description

Hi. I've come across an error in plotting that I am unsure how to diagnose. The data is a simple 2D temperature field. When I use the south pole projection, the contourf does not show values greater than about 260K. But if I use contour or pcolormesh, the values are shown. Furthermore, if I change from the 'splaea' to 'robin' projection, contourf shows all the values - as expected. What is causing the issue with contourf for 'splaea' projection? If I don't use proplot (just use matplotlib) I do not have this issue. Thanks!

Steps to reproduce

A "Minimal, Complete and Verifiable Example" will make it much easier for maintainers to help you.

Proplot version

Equivalent steps in matplotlib