Employee in arrears making changes to benefits, impacting retros

Summary:

Employee in arrears makes changes to benefits which then causes a retro and subsequently errors out

Content (required):

If an employee is in arrears and they haven't earned enough pay, the system will not take a deduction (which is fine). However, when that person makes a change to their benefits, it causes a retro which then compounds with the arrears and causes that person to error out. Normally our payroll team just overrides the retro, but is there a reason that the system treats the retro differently in that it tries to take out the full amount? Is there a simple fix that we can update the elements to disallow the retro to take out the full amount,