Rules for posting key & and acct & set incorrectly for "&" field

What causes this issue?

One of the rules specifies that the field demands a required entry, the
other rule says that the field is to be suppressed.

How to fix this error?

Correct one of the two rules for the field selection.
You find the field status group in the G/L account master record:
<DS:TRAN.FS02>Execute function</>
You can find the rules for the field status group in the Financial
Accounting Implementation Guide in the activity
<DS:SIMG.SIMG_CFMENUORFBOBC4.SIMG_ORFB1>Maintain field status
variants</>.
You can find the posting key in the Financial Accounting Implementation
Guide in the activity
<DS:SIMG.SIMG_CFMENUORFBOB41.SIMG_ORFB1>Define posting key</>.

Error message extract from SAP system. Copyright SAP SE.