Timesheet retrieval process

We are following a process wherein we import thet auto-approved timesheet everyday. Though we are noticing a problem.

Enter a timesheet on Monday and import it, works fine

Enter a timesheet on Tue and import it, it reverses Monday and re-imports Monday as well as Tue, so for Tue I have 3 transactions

Enter a timesheet on Wed and import it, it reverses Monday and Tue and re-imports Mon, TUe as well as Wed, so for Wed I have 5 transactions.

So for just 3 days, rather than having 3 transactions I now have 9 transactions. Is there a way to stop this or any idea what is causing this