&1 &2 is locked by user &3

What causes this issue?

There are two possible causes:
You want to edit object &V2& (&V1&). However, user &V3& is using it at
this time.
You want to carry out a function that would result in a change to an
object (&V1&: &V2&). However, user &V3& is editing the object at this
time. Until user &V3& has saved the changes and left group maintenance,
you cannot execute the function for the object.

How to fix this error?

If you are locking yourself, go to the screen in which you are also
editing the object.
Otherwise, contact user &V3&. Note the <DS:TX.RKS_ENQ_NODES>validity
rules</>.

Error message extract from SAP system. Copyright SAP SE.