Capped holiday for flexible employees

Hello, 

Is there a reason when an employee is moved from Hourly to Salary (or vice-versa), the system re-calculates the Annual Holiday Allowance. When doing this, despite the 'Maximum days allowed' box being ticked and capped for employees to not have more than 28 days holiday, the recalculation is showing more than 28 days holiday for these employees. 

Is there a way to prevent any Flex employee from getting more than 28 days, despite if we change their pay type at some point?

Thank you.