Maximum number of & items reached

What causes this issue?

For this document, you have already entered more than the maximum
number (&V1&) of items.

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?

INCLUDE MB_NA_MAX_POS_VORGEHEN

Error message extract from SAP system. Copyright SAP SE.