Duplicate records created when users submit time sheet from time sheet portal

[Alia]

Duplicate time card records created when users submit time sheet from time sheet portal and it shows in the resource aggregate table with the same short description and same project code. 

Any suggestion why this is happening?

[Mark Manders]

Is everything fully OOB on your instance or has anything been customized for any reason? On my OOB instance, this doesn't happen, hence me asking.