fontforge/fallback creates incorrect file names

[pgundlach]

E:  [page 1] Failed to load font FrutigerLTStd-Light.otf 
·   Create font metrics (name=texgyreheros-regular.otf,size=10,id=1,mode=fontforge)
·   Create font metrics (name=FrutigerLTStd-Light.otf,size=10,id=9,mode=fontforge)
E:  [page 1] Failed to load font FrutigerLTStd-Light.otf 
·   Create font metrics (name=FrutigerLTStd-Light.otf,size=10,id=9,mode=fontforge)

not the correct file names

<Layout xmlns="urn:speedata.de:2009/publisher/en"
    xmlns:sd="urn:speedata:2009/publisher/functions/en">

    <LoadFontfile name="fl" filename="FrutigerLTStd-Light.otf">
        <Fallback filename="Arial.ttf"/>
        <Fallback filename="symbol.ttf"/>
        <Fallback filename="cmunss.ttf"/>
    </LoadFontfile>
    <DefineFontfamily fontsize="10pt" leading="12pt" name="text">
        <Regular fontface="fl"></Regular>
    </DefineFontfamily>

    <Record element="data">
        <PlaceObject>
            <Textblock>
                <Paragraph>
                    <Value>Hello  λ.</Value>
                </Paragraph>
            </Textblock>
        </PlaceObject>
    </Record>
</Layout>

version 4.19.19