Postgresql sequence always 1
What you want is how sequences in PostgreSQL generally behave.

You must have some rogue process which is issuing a command such as:

alter sequence client_id_seq restart;


Or something equivalent to that.  Figure out what is issuing that command, and make it stop.

If you can't figure out who is sabotaging your sequence, there are a variety of ways to figure it out.  One is to crank up your log level by setting log_statement to 'ddl' or 'all', and look in the logs.  Another is to make your table and sequence owned by a role which does not normally log into the database, and grant rights to the table and sequence to the normal log-in users.  They will then get errors when they try to reset the sequence, because only the owner can do that.  (This is a good practice anyway, to have objects owned by special roles which do not log in except when it is necessary to change the schema.)