When an entity is edited on a master or standalone server, its now outdated entry is removed from the memcached cache (this doesn't always work properly, MBS-7241, but in principle). However, on a slave server, when an entity is changed by a replicated update, its cache entry is not invalidated. The server may use the outdated version indefinitely. - Obviously, this only affects replication users who actually run the web server.

It's not obvious what should be done to address this. One option would be to invalidate the cache from the import script; obviously, this would have to be configurable.