Confirmation type reset to assembly confirmation

What causes this issue?

You were in the make-to-stock scenario with backflush type component or
activity backflush and switched to another scenario using the tab
pages. However, only the assembly backflush is allowed for
make-to-order production or production by lots.

System Response

The system automatically switched to the assembly backflush.

Error message extract from SAP system. Copyright SAP SE.