Steps to reproduce:
1. Open Orders app.
2. Press 'New' button to open 'Create Purchase Order' form or select any Purchase Order and press 'Edit' icon to open 'Edit Purchase Order' form.
3. Press '+' button to add a Vendor.
4. Select any Vendor from the search results list.
5. Try to change vendor using '+' button again.

Actual Result:
No Vendors shown in search results if you try to access it more then one time.
Note: the list of Vendors is back if you play with filters and use "Reset All" option or if you refresh the page.

Expected Result:
List of Vendors should be shown for a user to select Vendor immediately.