Hammer promote starts immediately on bash script without finishing 'publish' and terminates immediately due to a lock

I have hammer publish/ promote automated script which runs via a cronjob every night. Lately, 'hammer promote' doesn't start due to a lock from 'hammer publish' even though i have 'wait $!' for a 'hammer publish' statement. Is this some type of bug? Looks like 'Hammer promote' starts immediately and doesn't wait for 'hammer publish' . Has anyone encountered this type of issue?