I have a serialised object which is fetched from the database using getOption() on an admin page load for a custom plugin that pulls youtube videos from their API. The object contains the layout of the sidebar menu which the end-user uses to navigate between the various playlists of videos that are avaliable on the front end of the plugin.
Every 2 or 3 refreshes of the admin page causes getOption() to return an incomplete object. var_dump() reveals that the objects are of type _php_incomplete_class_object.
Generally when it starts returning an incomplete object it keeps doing it until I come back, some 15 or 20 minutes later.