Flag for 'no aggregation required' must be set due to formulas

What causes this issue?

The non-aggregation indicator was set to value 'X' by the system.
How the indicator is to be set, comes from the operators used
by the formula definition.
The indicator decides whether the value of the key figure in the results
row should be calculated for each drill down level (side) on account of
the formula, or whether the key figure can be calculated from the
underlying line items. You can find further information by using the F1
help for the field.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Error message extract from SAP system. Copyright SAP SE.