why some of my staff's hours goes on the next day if they clock out after midnight. Again, it only happens with some of them

Hi @Mauro Tondo​ If this is only happening for some staff that are scheduled after midnight and not all, I would suggest raising a case via the community. You should see the option under your account on the right of the search bar.

You can check the Rota global settings to see if Bypass shift validation on Rota start and end times is set to no. Changing this to yes may solve the problem.

Kind regards

@Debbie Thomas​ 

Fourth