Why do time entries get stuck in AFRV table instead of going to the target component (service order)?

During transfer of time entries from Catsdb table to the target component (service order), sometimes some time entries get stuck in confirmation pool (AFRV table) and will not be posted to the service order. These entries can be cleared manually through t.code IW46 and posted to serice order. Please help me to know why the time entries sometimes are not posted to service order through transaction cat9 and get stuck in AFRV table needing to be manually cleared. Please note that it is a background job used for the Order closure process and cat9 is a part of it. This question is relevant CS. But as I could not find the relevant forum, I have posed this question here. Please help. One of the answers i found is the authorization issues or posting date being in the future. Please also let me know how authorization can be an issue in a background scheduled job.