There is an odd behavior of child instances that have been spawned by a now suspended process instance.

For example, a case instance `B` initialized by a callActivity of a now suspended process instance `A` can be worked on (complete humanTasks etc.) but may not be completed. The following error is triggered:

Error while completing sub case of case execution 'CaseInstance...'.
Reason: 'ENGINE-03043 Execution with id '#...' is suspended.':

I understand that this is caused by the suspension state of the parent process instance but the behavior isn't coherent. If a user is able to work on some tasks of the child instance, every step of the child's lifecycle should be available. From a user perspective it's unclear why the self-contained unit of work of `B` can't be completed. The user may not even know that `B` is a nested execution of `A`.

Reactivating `A` should probably trigger a check if the underlying process/case instance `B` of the callActivity has completed while it has been suspended. That's the moment `A` may continue marking the callActivity as complete.

I found the following open tickets related to suspending/activating case instances.

As CaseWorker I can suspend an active Stage, Task or CaseInstance (#CAM-2461)
As CaseWorker I can resume a suspended Stage or Task (#CAM-2462)

#CAM-2462 describes the same desired behavior while resuming a case for caseTasks and processTasks as I was expecting in the context of a callActivity.