Multi instance activity triggering message start event in same process - whats the best way to design

BPMN & Modeling
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1

Hi Team,

I have a process where manual trigger initiates item update in multi instance loop.
This loop triggers message event (identified as ItemRuleUpdated in attached bpmn).
items can be in 1000s or 100k+. Currently, the multi instance loop is able to trigger ~300 instances of message event only.
What could be better way to design the process or is there any config to allow the triggered message event count to be higher.
Process attached. Event_15tfwll triggers the flow in another swimlane where message is caught by ItemRuleUpdated eventID.

itemUpdate-sampo.bpmn (33.4 KB)