This error normally occurs, when the sequence PCM_COUNTER_PM_SEQ is lower than the maximum number of the PM in the system.
Possible reasons for the issue to occur is if the user is using another way (data migration etc..) to create PM actions and also manually feeding the PM no without using the sequence.
As per the solution you need to change the PCM_COUNTER_PM_SEQ to max value of the pmno+1 from database. If you are using any migration jobs to create PMs then you need to change the pm no to fetch from the sequence. If you are giving pm no manually then you can use the query Select MAX(PM_NO) from pm_action_tab; to fetch the next pm_no value to give and you need to update the sequence also for the next value otherwise error may occur repeatedly.