Please tell employees to report immediately if punch does record. In case of two or three instances you can ask the employee to re-register another finger for bio-metric punch. In our organization we are 4K employees are using.It is working fine.Else you can start attendance regularization by one single person who will be authorized to regularize one's In-Punch. Please monitor whether any person is using regularization for In-Punch only, then confront him. I think this will work