Process errors leads Command to be executed again when using the async work item handler in JBoss BPM Suite 6

Issue

The Asynchronous processing in the BPM Suite has general problem with the command execution.

The AbstractAvailableJobsExecutor executes the user command on the line 122:

ExecutionResults results = cmd.execute(ctx);  

And at the same time JBPM database changes. But if there is an exception after user command execution the whole execution process (also user command) will be executed again.

For example we have the AsyncWorkItemHandler to send an email:
1. Call the command to send an email.
2. Some error happened after the command was executed;
3. Handle the exception and execute the whole job again (Retry).
Problem:: We going to send the email again.

Could you provide us with a solution to separate the execution of the command and the BPM Suite database changes in the job executor?