Troubleshooting Mixpanel: Unregistered Signup Events in Web System

Hi, I have an event called "Signup" implemented to track all new accounts in my web system. Currently, I also have a backoffice where I manage all new accounts for my users (Account info like suscription info, payments, active users, etc...). A very strange error is happening in Mixpanel, randomly the "Signup" event is not registered, therefore, at the end of the month when I check the number of new accounts in my Backoffice and Mixpanel report, they do not match. This is super strange, because it is the only event with which I have this problem. Any ideas how to resolve this issue? Signup event implementation