Random false network posts updates - incorrectly appearing as lest network posts

Hi there,

My site http://retrofitdiaries.org has worked for a while, but I'm getting problems with random updates - for instance the latest network post was not actually updated since more than a year ago but suddenly was featured as the 'latest'.

This is happening quite regularly - about once a week perhaps, seemingly at random from anyone in the network.

This maybe a database issue, or to do with the theme, I can't tell. Either way I don't know how to fix this!

Have updated to latest everything - Buddypress, WP, Network etc. etc. makes no difference...

Help appreciated....