For a very specific geometry, it is possible to do curvedsky.map2alm when the map is initialized, but not after writing to disk and reading it back in, even though the map that has been read in seems identical in every respect to the original map. This bug is demonstrated in this notebook:
https://github.com/msyriac/orphics/blob/master/scripts/EnlibCurvedSkyWriteMapBug.ipynb