Calculate Seniority Date process not running for all employees

Summary:
We have approximately 23,000 employees and utilize five different seniority date rules. We have the Calculate Seniority Date process scheduled to run on a daily basis (with a lookback of 36500 to refresh all of our employees.) However, we have noticed that after the process completes, not all of our employees show an updated date on their seniority dates page. As of this morning, about 11,000 of our active employees have not been refreshed/updated in the last 48 hours.

Is there a background limit on the number of users the Calculate Seniority Date process can handle before it just stops running? I do see it is breaking up the process into dozens of subprocesses to process employees in smaller chunks, but we need the process to run for all employees on a daily basis in order for the dates to reflect correctly, as well as the 'Length of Service' calculations the system displays.