Thanks for sharing your concern with us, @Skeptic. 

I've got your back! Let me share some troubleshooting steps to get this sorted out.

There might be an issue with your company file's data that's causing the closed sales orders to appear on the Open Sales Order report. I recommend running the Verify/Rebuild tool. Verifying it will detect any damaged data and fix it by rebuilding. It also allows your QuickBooks software to refresh the data inside the company file. 

Beforehand, make sure to create a backup copy. If there are changes that occur, having a copy allows you to restore it to undo the changes.

Follow the steps below on how to verify data:
 

1. On the top menu, click File.
2. Choose Utilities.
3. Select Verify Data.
   
4. Click OK when you see the message, QuickBooks detected no problem with your data.
5. If Verify finds an issue with your data, you'll be prompted to Rebuild Now or View Errors.
6. Click Close or View Errors and take note of the specific error message.

Next, here's how to rebuild data:
 

1. On the top menu, click File.
2. Choose Utilities.
3. Select Rebuild Data.
   
4. Click OK if you receive a prompt to back up your company file.
5. Click OK when you get the message, Rebuild has completed and proceed to the next step.
6. Run Rebuild Data again to make sure there's no error.

Additionally, it's best to make sure your QuickBooks Desktop is up-to-date. This way, you always have its latest features and fixes. 

Keep me updated on how this works on your end. I'm determined to help you succeed. Take care always, @Skeptic!