If at the beginning of the year someone enrolled in an annual plan has an FTE of 1.0, they get the full allowance for the year. If half way through the year their FTE changes to 0.5, their allowance should be reduced to 75% of the full allowance. This doesn't happen even if accrual is deleted and regenerated.

For companies with short accrual periods the difference this inaccuracy amounts to but in companies with Annual accrual periods, which is most of them in the UK, this discrepancy is massive.