Usually, QuickBooks won't auto-populate and overwrite the next line of a timesheet once the previous one is set.
Since this is an odd behavior, please try refreshing the page and logging out and back in. Then, go to the Weekly timesheet tab again to see if it won't overwrite anymore.
If the issue persists, use an incognito window to start a fresh session without any cache or cookies that could cause the problem. You could also switch to a different browser as another option.
Feel free to comment below if you have any additional questions.
