Output-Mapping doesn't work right in a Transaction Subprocess

Hello together. I have a problem with my transactional subprocess.

Description:
I have defined in the Test-Scope “varGlobal” and inside the Transaction-Scope “varLocal”. When the Transaction Subprocess is done, the value of “varLocal” should be mapped on “varGlobal” and afterwards the process should end.

Problem:
When I try to end the process, than I get this error:

An error happened while submitting the task form :
Cannot invoke "org.camunda.bpm.engine.impl.persistence.entity.ExecutionEntity.delayEvent(org.camunda.bpm.engine.impl.pvm.runtime.PvmExecutionImpl, org.camunda.bpm.engine.impl.core.variable.event.VariableEvent)" because "scopeExecution" is null

My Assumption:
While searching for the reason, I have found out, that this error only happens, if I have a Rollback-Task and the Output-Mapping. If I remove one of them, than everything works fine. I have also checked the Camunda-Cockpit:

The scope of the variables is somehow messed up, because it shouldn’t be possible to see “varLocal” in the “Show variables”-Task.

This is the BPMN-Diagram:
Test.bpmn (6.4 KB)

Is this a bug or do I do something wrong? Thank you for your answers in advance.