Sub process is creating multiple threads when execution delay

ACT_RU_JOB column rev_ is 18.
BPMN file contains setup starting variable Service Task with Async after and Exclusive checked. which further have sub process. At some interval sub process is initiated from beginning again and again when delay of execution sub process → service task happens.
Tried & Tested :- Retry tried to 0 still sub process is going on creating new thread and execute from beginning.
Errors:- ENGINE-03005 Execution of ‘DELETE MessageEntity[257532d4-2f9a-11ed-a9c7-64bc5824e830]’ failed. Entity was updated by another transaction concurrently.