INSERT .. WHERE + GRAPH leads to server error

Virtuoso Universal Server RDF Data Management
2

Using my latest Virtuoso Version 07.20.3237-pthreads for Linux as of Sep 26 2023 (ec28543a2) binary, if I insert at triple to match your search condition ie

INSERT INTO GRAPH <http://example.org> { <1> rdfs:label <3> }

Then run your query via a Virtuoso ~/sparql-auth endpoint as the dba user ie

INSERT {
    GRAPH ?g { ?s <http://acme.org/what#ever> "abc" . }
}
WHERE { GRAPH ?g { ?s rdfs:label [] . } }

The query runs successfully without any error and inserts the ?s <http://acme.org/what#ever> "abc" triple pattern in the graph ie

s p o
1 http://www.w3.org/2000/01/rdf-schema#label 3
1 http://acme.org/what#ever “abc”

Thus, what are the version, gitid, build date etc of your Virtuoso build which can be obtained as detailed at Interrogating attributes of a Virtuoso Server instance via SPARQL ? And was is the simplest test case you can provide for recreating the problem ?