Gaps are cleaned without being processed

Hello, We are using axon framework in project with postgres sql for event store.
We are using default setting of hibernate with allocationSize set to 50 and have 5 instances of the application running.
We see that some of the events in domain event entry are not getting processed.
For instance, we have token value at 2501 with gaps [2401,2402, 2410…2499] and domain event inserted at index 2403. As per our understanding since it is not part of the gaps array it is not getting processed.
Would like to understand the instances this may happen? Why would some ids got cleaned even after not processed and within the gap threshold window