Unit &1 does not correspond to dimension &2

What causes this issue?

Bulks and basic materials can be nested. However, the unit must match
the dimension.
If a product contains a basic material or a bulk in the composition, the
unit has to be in grams on the first level and percent on further
levels. Other units of the same dimension can be used too.
If a bulk contains a basic material, the unit has to be percent or a
unit with the same dimension.

System Response

The system stopped processing.

How to fix this error?

Check the product structure for nested basic materials and bulks.
Note: A basic material in a composition of a bulk needs percent as unit.

Error message extract from SAP system. Copyright SAP SE.