1) First step is to modify the POS operation type. To do so, go in Inventory - Configuration and Operation types. 

Select the "PoS orders" operation type, and modify the traceability options, turn off:

- Create New lots / Serial numbers

- Use existing lots/serial numbers 

2) The second step is to modify the location of products concerned by the issue. 

To do so: Inventory - Configuration - locations and select the removal strategy you want to apply. 

In order to see this option (Removal strategy), you need to activate the option "Multi-steps routes" in the Inventory configuration. 

Once it is done, the products in the location will be automatically selected in POS and the lot numbers will be assigned depending on the removal strategy you set up.