Assignment in Internal move raises: The field "Unit Price" on "Stock Move" is required


I created an Internal Shipment with the Order Point > Supply Stock wizard.
When changing its state to Assign, it raises The field "Unit Price" on "Stock Move" is required.
I cannot find a Unit Price field that would be missing in those products. What does this message mean?

This is very strange because the invisible and required states are the opposite of each others.
Also it is not required between storage locations which should be only storage or lost_found.

From and to locations are both storages, though on different warehouses.

Then maybe it is the transit location. Any way you must check the location of the moves.