This sounds like a repeating job/group with new occurrences. Check out the Options tab for both group and job-levels
Group Options, If job is running, then Run Anyway
Job Options, If job is running, then Run Anyway
The correct setting should be:
Group Options, If job is running, then Run Anyway
Job Options, If job is running, then Defer until Normal or Defer Until Complete
which means if any of the deferred options are selected, the second occurrence will wait until job is completed normally (Defer Until Normal), or wait until job either completes normally or abnormally (Defer Until Complete)
Now I wonder what causes the second instance to complete normally and not the first instance.
BR,
Derrick Au