When we clone our production instance to staging, we restore the database with updated host information prior to restoring the database.
Querying a smart group returns all contacts in database, not just those in the smart group. Running the Rebuild Smart Group Cache scheduled job does not do anything.
Note I DO recommend running the job that flushes expired groups by scheduled job - just not the one that rebuild them all, even the ones you don't really need
Where is that job?