Explanation
Drip feed dispatching is a feature that allows dispatching service appointments gradually throughout the day based on a drip feed rate defined for each service territory or resource. If other scheduled jobs are dispatching appointments and exceeding the drip feed value, then the drip feed dispatching will not trigger as expected.
The appointment status going from Scheduled to Completed or being Canceled, Completed, or Cannot Complete does not affect drip feed dispatching, as these are valid status transitions for dispatched appointments. The default drip feed setting does not override the drip feed rate on a service territory, but provides a fallback value if no rate is specified on the territory or resource level. References:
https://help.salesforce.com/s/articleView?id=sf.fs_drip_feed_dispatching_overview.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.fs_status_transitions.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.fs_drip_feed_dispatching_settings.htm&type=5