Incorrect carryover expiration (reoccuring issue)

Summary
Multiple Employees have incorrect carryover expiration

Content (please ensure you mask any confidential information):

Hi,

We have our carryover set to expire at the end of April but we have multiple employees (around 10% of the company) who have the wrong value in their carryover expiration.

We are using seeded functionality (no carryover in fast formula) and there is no logic I can see in the expiration, if I withdraw the accrual as of the end of last period and recalculate the accrual the issue is resolved, but it then reoccurs within a couple of days, the diagnostic reports show no issues with the absence record of the inviduals.