I admire you for getting back on this thread, @kvanheuk.

I appreciate the screenshot you've provided. Thus, this helps us get on the same page when sorting out your concern. Please know that my colleague already updated her response above to clarify things.

Based on the visual reference you've provided, it's likely that the Hourly cost rate of the vendor was updated on the vendor profile after creating the Weekly timesheet. That said, the cost rate was unable to show the updated information. However, it'll show up in the next time range. 

That's why erasing the assigned project and adding it back in on the timesheet won't let you see the information. 

To get around this, we can manually enter the cost on the individual timesheet.

Otherwise, we can delete and recreate the affected weekly timesheet. 

For more information, I'll add this resource again to help you use projects to track your labor costs and profitability: Track hourly labor costs and profitability by project in QuickBooks Online. 

Click the Reply button if you need more help organizing your projects or any QuickBooks-related concerns. Take care and have a pleasant day.