If you use a search API call for a Sedol it will return all RICs.

If you use a composite extraction request API call for a Sedol it will return the primary RIC.

LP71000002 is the primary RIC for Sedol B1YW440 (the RIC for the instrument quoted on its primary exchange).

More details on this, and (Java) code samples can be found under query Is there JAVA examples to look up a RIC by CUSIP, ISIN or SEDOL?

Would it be possible to get the request date and time (in UTC) and the DSS account number please? I can take a look in the log tomorrow US daytiem hours and see what happened.

That is not what I am seeing this morning - What I may need more than anything is your validation request - or... was the observation about a search request maybe?

<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
    <s:Header>
        <h:CredentialsHeader xmlns:h="http://reuters.com/datascopeselect/ExtractionService/v1/" xmlns="http://reuters.com/datascopeselect/ExtractionService/v1/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
...
        </h:CredentialsHeader>
    </s:Header>
    <s:Body xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
        <ValidateInstruments xmlns="http://reuters.com/datascopeselect/ExtractionService/v1/">
            <request>
                <PerformExpansion>false</PerformExpansion>
                <Identifiers>
                    <InstrumentIdentifier>
                        <IdentifierValue>B1YW440</IdentifierValue>
                        <IdentifierType>SED</IdentifierType>
                    </InstrumentIdentifier>
                </Identifiers>
                <IncludeDetails>false</IncludeDetails>
            </request>
        </ValidateInstruments>
    </s:Body>
</s:Envelope>

<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <soap:Header>
        <CredentialsHeader xmlns="http://reuters.com/datascopeselect/ExtractionService/v1/">
...
        </CredentialsHeader>
        <OperationInfoHeader xmlns="http://reuters.com/datascopeselect/ExtractionService/v1/">
            <Host>01</Host>
            <ProcessingTime>00:00:00.7235389</ProcessingTime>
        </OperationInfoHeader>
    </soap:Header>
    <soap:Body>
        <ValidateInstrumentsResponse xmlns="http://reuters.com/datascopeselect/ExtractionService/v1/">
            <ValidateInstrumentsResult>
                <Instruments>
                    <ValidatedInstrument>
                        <IdentifierValue>B1YW440</IdentifierValue>
                        <IdentifierType>SED</IdentifierType>
                        <Source>LSE</Source>
                        <AssetId>0x0003dd0015032be3</AssetId>
                        <QuoteId>0x0003dc0047918188</QuoteId>
                        <Segment>E</Segment>
                        <ObjectType>EQQU</ObjectType>
                        <Ric>III.L</Ric>
                        <FileCode>0691</FileCode>
                    </ValidatedInstrument>
                </Instruments>
                <UnmappedIdentifiers />
                <UnmappedIdentifierErrors />
                <Details />
            </ValidateInstrumentsResult>
        </ValidateInstrumentsResponse>
    </soap:Body>
</soap:Envelope>

A Sedol (like an ISIN) can expand into several RICs. It is up to the querying application to handle all of them. A search for Sedol B1YW440 will return 9 instruments, including III.L (an equity) and LP71000002 (an MTLF).

If you share the query parameters, and preferably the code snippet that sends the query and handles the result, we can investigate why you only get one.