Form & is still active (CLOSE_FORM missing)

What causes this issue?

The function OPEN_FORM has been called for layout set &V1& although
the previous print procedure was not ended with CLOSE_FORM.

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

System Response

How to fix this error?

Please check the use of the SAPscript program interface in your
program. A print procedure must be initiated with OPEN_FORM
and ended with CLOSE_FORM.<ZV>(_BS:aus TD420 kopiert)</>

Error message extract from SAP system. Copyright SAP SE.