AP Invoice is automatically suppressed

Hello,

I would like to inquire about abnormal behavior that I have encountered in the AP invoice approval process. We have 3 stages: first, the manager of the submitter; then the cost center manager; and finally, the project manager.

If the invoice is not associated with a project (project number is null), then it is automatically suppressed by the manager of the submitter and approved in his name without him even receiving an FYI notification. is there any idea why?