I maintain the pi3d package which is available on pypi.python.org. Prior to v2.8 the latest version was always returned by a search for 'pi3d'. Subsequently v2.7 + v2.8 then v2.7 + v2.8 + v2.9 were listed. These three are still listed even though I am now at v2.10. i.e. the latest version is NOT listed and it requires sharp eyes to spot the text on the v2.9 page saying it's not the latest version!
NB all old versions are marked as 'hidden' I have tried lots of different permutations of hiding and unhiding releases, updating releases, switching on and off autohide old releases, editing the text of each release etc ad infinitum.
Is there some obvious cause of this behaviour that I have missed?
Yes, it's just a problem with the pypi search engine, like Khush said.
on pypi.python.org what would cause hidden old versions to be returned by explicit search