Let me get you back on track, @jerseydane.
Based on your scenario, the auto-fill feature is likely the cause of the prompts or pop-ups. Thus, you'll notice that QuickBooks will pre-fill the info when selecting a vendor or customer.
In your case, they're not duplicate inventories or entries. I know how to disable this option to get you back up and running again. Let me guide you how:
- Click Edit, and then choose Preferences.
- Select General, and then My Preferences.
- Go to the Automatically Recall Information section.
- Make sure to uncheck the Automatically remember account or transaction information box.
- Click OK when you're ready.

Once turned off, you can perform the usual steps you normally would to enter your inventory or manage your vendors.
In case you observe some mismatch in your inventory reports, you can use this helpful article to resolve them: Fix balance Sheet and Inventory/Stock Valuation reports discrepancies.
Also, you can run other inventory-related reports in QuickBooks. To do this, you can go to the Reports menu. Then, select the desired report from the Inventory section.
I can always provide you additional inventory insights in QuickBooks. Just comment back below so I can assist you right away. Have a great day!