How to recreate:

1. Go to registration page "/corporate/customer-portal/register"
2. Register account
3. Go to list of applications
4. Reject created application
5. Go back to registration
6. Create new account with different data
7. You should get a screen with information that: 

Registration is currently locked.

As a security measure, registration is locked for another 5 minutes to prevent malicious behaviour.
Please, try again later.