Error when adding to multi-instance sub-process

I am wishing to add another instance to a sequential multi-instance sub-process using the technique described here: Modify Multi-Instance Process

I am receiving the following error: Concurrent instantiation not possible for activities in scope SequentialUpdateSubProcess#multiInstanceBody

The modification is being performed by a script. The relevant lines:

.setVariableLocal(“event”, eventJsonValue)

This succeeds if the sub-process is parallel-multi-instance. I suspect it is trying to start the new instance immediately, rather than after the intial instance completes. Is there a different technique to add to a sequential multi-instance activity? I have attached the model.

OrderUpdateRunner.bpmn (9.2 KB)

For anyone in a similar situation, we determined that it is not possible to add an instance to a sequential multi-instance activity using the process modification technique referenced above. We decided that it is easy enough to model a sequential invocation ourselves and that’s what we did. We track our own collection and ‘loopCounter’. Revised bpmn attached, with embedded scripts.

OrderUpdateRunner orig.bpmn (16.2 KB)