Purchase document is allocated to asset & &

What causes this issue?

The asset number &V1& &V2& assigned in the purchase document

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

is different from the asset number entered manually
cannot be transferred, because the 'Asset number' field was hidden for
the account in question

System Response

In the first instance a warning appears, drawing your attention to the
different account assignments. In the second instance an error message
appears, because the asset number must be transferred from the purchase
order but the necessary field is hidden.

How to fix this error?

If you receive the warning, check which asset number is the correct
number for this down payment.
If you receive an error message, you must either choose another special
G/L indicator for down payments so that it is possible to assign an
asset number to the relevant general ledger account, or you must change
or delete the the specified purchase document number. Only those
purchase documents are allowed which are not assigned to assets.

Error message extract from SAP system. Copyright SAP SE.