The message "Duplicated schedule events skipped" on shipments within Shiptheory is not cause for concern, it is purely informational. The message means that the shipment was due to be processed through the automatic shipping rules, however via a rule schedule, however, at the time it was due to process, more than 1 conflicting schedule events were found for the same shipment.
This can happen if you retry the shipment several times, or resend the shipment from your sales channel several times, and it matches a shipping rule each time with a schedule attached. When duplicated shipment schedule events are found, the most recent schedule is respected and the others ignored.
For more information on how to use shipping rules to schedule or delay shipments, please read our shipping rules schedule guide or reach out to support.