Stock value and qty are unrealistic: & / & -> see long text

What causes this issue?

The system has detected data inconsistencies in the material master
record: &V1& / &V2&
Examples:
negative stock value for a positive stock quantity
positive stock value for a negative stock quantity
negative stock value for a positive sales value
positive stock value for a negative sales value

System Response

The system does not allow further movements for this material until
the data inconsistencies have been corrected. Any further movement
could lead to even greater inconsistencies.

How to fix this error?

INCLUDE MB_NA_HOTLINE

Error message extract from SAP system. Copyright SAP SE.