Do not run imports or exports while Quantity Breaks are active. Importing products while Quantity Breaks is active will overwrite meta-field data required for proper operation.
Quantity Breaks creates variants for the different price levels, and if you do an export or import, you can override those. Even worse, it can make it so the app loses connection with those items if the import overwrites a products meta-fields, which is almost always the case.
Visit Delete Quantity Breaks Variants for the complete instructions.
The Quantity Breaks (standalone) app is no longer available for new installations. If you are currently using Quantity Breaks (standalone), you will be able to continue using the app on a grandfathered plan.
Any new installs of the Quantity Break app will be redirected to Custom Pricing which has a Quantity Breaks plan available. For more information on Custom Pricing, please visit Custom Pricing: Information and Overview.