Question about restrictions behind a task flow form

We have a form created using HRMS task flow. The form uses "Combined Person & Assignment Form". The form works for some retiree records and not for others. The message says "invalid value for the field employee_number". I would like to find out if there is any filtering condition being used in the task flow form which prevents some of the retiree records from showing. I could access all those retirees from the regular people and assignment form without any issues. I'm not sure if there is any security profile that is preventing the data either. Any help in figuring