DB update transaction concurrently issue

Hi Team,
Am getting below issue while processing my txn. Please help me to solve this issue.

ENGINE-03005 Execution of ‘UPDATE VariableInstanceEntity[8e5f4a82-89ca-11ea-a925-0242ac1e7c30]’ failed. Entity was updated by another transaction concurrently

My Flow like this:

start —> service task → user task–>usertask–>end.

My Java version 11 and Oracle 11gR2

com.oracle ojdbc8 12.2.0.1 runtime