Disc. document & & is blocked by user & and can only be displayed.

What causes this issue?

Discount document &V1& &V2& is currently being processed by another
user. This means that the document which is displayed at the moment
could also be changed. To avoid inconsistencies, you cannot make any
changes to the document which is currently displayed.

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?

DEFINE &USER& = &V3&
INCLUDE MESSAGE_ENQUEUE_USER OBJECT DOKU ID TX
When the other user has finished working on the document, you can
restart the transaction and make changes to the document.

Error message extract from SAP system. Copyright SAP SE.