Select "Subject" for the search type (or any search type - they all seem to generate an error when quotes or backslash are included)
into the search box there should be no error message (the backend will ignore these characters when the = operator for a full-text search is used, for an exact search using == correct masking is needed).
Actual result for the second search term: Error popup: ERROR: in module @folio/inventory, operation GET on resource 'records' failed, saying: org.z3950.zing.cql.cql2pgjson.QueryValidationException: org.z3950.zing.cql.CQLParseException: expected ')', got EOF
These are the query strings (after urldecoding) sent from front-end to back-end:
They should be
For CQL quoted string masking see https://www.loc.gov/standards/sru/cql/spec.html#bnf