Object locked for processing with change number &

What causes this issue?

You want to edit an object with change number &V1&. However, this
change number contains the indicator which blocks the object type or a
specific object for this change number.

How to fix this error?

If you are authorized to change the change master, delete this
indicator for the object type concerned. Otherwise, consult your system
manager.
If the change master cannot be changed, choose a different change
number which allows changes for this object type.

Error message extract from SAP system. Copyright SAP SE.