Formal error in table &1: Item &2 with two tax codes

What causes this issue?

Both the tax code for tax on sales/purchases (MWSK) and the code for
other taxes (STEKZ) are specified in a G/L item (FKKOPK) Steuern
(STEKZ). However, you can enter only one of these two tax codes.

System Response

Error message causing processing to be stopped.

How to fix this error?

INCLUDE NA_SYSADMIN1 OBJECT DOKU ID TX

Procedure for System Administrators

INCLUDE FICA_NA_OSS OBJECT DOKU ID TX

Error message extract from SAP system. Copyright SAP SE.