Why can't I load a WFS into Openlayers: "TypeError: null is not an object (evaluating 'Ob(d).b')"

Question

I am teaching myself the use of Services (WFS) in and OpenLayers itself. As far as I know I managed to get a proper gml-file (GML2, I hope [EDIT: It is GML 3.1, I figured]) from a governmental server by calling the following url:

https://www.wfs.nrw.de/geobasis/wfs_nw_atkis-basis-dlm_aaa-modell-basiert?service=WFS&version=1.1.0&srsName=EPSG:25832&request=GetFeature&typeName=adv:AX_Strassenachse&bbox=391918,5709660,393499,5710570,urn:ogc:def:crs:EPSG::25832&fin=fin

(I can get a GML3.2-File by using this url instead, but I think OL can't handle that)

var utm32nName = 'EPSG:25832';
proj4.defs(utm32nName, "+proj=utm +zone=32 +ellps=GRS80 +units=m +no_defs");
utm32n = ol.proj.get(utm32nName)
var wfsSource = new ol.source.Vector({
    format: new ol.format.WFS({gmlFormat: ol.format.GML3 }),
    loader: function(extent, resolution, projection) {
        var url = 'https://www.wfs.nrw.de/geobasis/wfs_nw_atkis-basis-dlm_aaa-modell-basiert?service=WFS&' +
              'version=1.1.0&srsName=EPSG:25832&request=GetFeature&' +
              'typeName=adv:AX_Strassenachse&' +
              'bbox=' + [391918,5709660,393499,5710570].join(',') +
              ',urn:ogc:def:crs:EPSG::25832&fin=fin';
        console.log(url);
        $.ajax({
              url
        }).done(
                loadFeatures
        ).fail(
                function(err, txtstatus) {
                   console.log('something went wrong')
                   console.log(err)
                   console.log(txtstatus)
                }
        );
    },
    strategy: ol.loadingstrategy.bbox
});
var loadFeatures = function(response) {
    //console.log(response)
    wfsSource.addFeatures(new ol.format.WFS().readFeatures(response));
    console.log(wfsSource.getFeatures());
};

var wfsvector = new ol.layer.Vector({
    source: wfsSource,
    style: new ol.style.Style({
      stroke: new ol.style.Stroke({
        color: 'rgba(0, 0, 0, 1.0)',
        width: 2
      })
    }),
    name: 'basisdlm'
});
fliederstrasse = [7.453175, 51.531939];
fliederstrasseWebMercator = ol.proj.transform(
    ol.proj.fromLonLat(fliederstrasse), 'EPSG:3857', 'EPSG:25832'
);
map = new ol.Map({
    layers: [
        wfsvector, 
        raster
    ],
    target: document.getElementById('map'),
    controls: ol.control.defaults({
      attributionOptions: {
        collapsible: false
      }
    }),
    view: new ol.View({
        projection: 'EPSG:25832',
      center: fliederstrasseWebMercator,
      maxZoom: 19,
      zoom: 17
    })
});

At

new ol.format.WFS().readFeatures(response)

I get the Error from the Headline and deep inside in ol.js in Ob(d).b it handles the srs-string, as far as I can tell. At some point in me working (don't know what I did, then), I managed to get no error, but nevertheless no feature has been loaded (0 features in source). Initially I tried to load the WFS with the url-attribute of ol.source.Vector() but that didn't work, either.

Even if I changed it to:

new ol.format.GML2().readFeatures(response)

or

new ol.format.GML3().readFeatures(response) //with different url

I got stuck at the same line in ol.js

Does anyone have a clue whats wrong?

I am not a native speaker of English.

---

EDIT: As requested in the comments, here is a small portion of the GML provided by the link above (and it seems to be GML3.1, not GML2):

<gmlx:FeatureCollection
    xmlns="http://www.adv-online.de/namespaces/adv/gid/6.0"
    xmlns:gmlx="http://www.opengis.net/gml"
    xmlns:xlink="http://www.w3.org/1999/xlink"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.adv-online.de/namespaces/adv/gid/6.0 http://www.wfs.nrw.de/aaa-suite/schema/old-gml-versions/3.1.1/NAS/6.0/schema/AAA-Fachschema.xsd http://www.opengis.net/gml http://www.wfs.nrw.de/aaa-suite/schema/old-gml-versions/3.1.1/NAS/6.0/schema/gml/3.1.1/base/gml.xsd http://www.isotc211.org/2005/gco http://www.wfs.nrw.de/aaa-suite/schema/old-gml-versions/3.1.1/NAS/6.0/schema/iso/19139/20070417/gco/gco.xsd http://www.isotc211.org/2005/gmd http://www.wfs.nrw.de/aaa-suite/schema/old-gml-versions/3.1.1/NAS/6.0/schema/iso/19139/20070417/gmd/gmd.xsd">
    <gmlx:boundedBy>
        <gmlx:Envelope srsName="urn:ogc:def:crs:EPSG::25832" srsDimension="2">
            <gmlx:lowerCorner>391831.345 5709517.376</gmlx:lowerCorner>
            <gmlx:upperCorner>393630.29 5710694.863</gmlx:upperCorner>
        </gmlx:Envelope>
    </gmlx:boundedBy>
    <gmlx:featureMember>
        <AX_Strassenachse gmlx:id="DENWAT01D0001uqC">
            <lebenszeitintervall>
                <AA_Lebenszeitintervall>
                    <beginnt>2015-12-06T19:58:47Z</beginnt>
                </AA_Lebenszeitintervall>
            </lebenszeitintervall>
            <modellart>
                <AA_Modellart>
                    <advStandardModell>Basis-DLM</advStandardModell>
                </AA_Modellart>
            </modellart>
            <istTeilVon xlink:href="urn:adv:oid:DENWAT01D000070p"/>
            <position>
                <gmlx:LineString srsName="urn:ogc:def:crs:EPSG::25832" srsDimension="2">
                    <gmlx:posList>
    392921.714 5709720.797 392991.374 5709731.245 392999.596 5709734.109 393006.221 5709739.54
    </gmlx:posList>
                </gmlx:LineString>
            </position>
            <anzahlDerFahrstreifen>2</anzahlDerFahrstreifen>
        </AX_Strassenachse>
    </gmlx:featureMember>
    ...

Answer 1

I found out, what the problem was, after switching from ol.js to ol-debug.js (should have done this earlier!).

This issue isn't in the WFS/GML3 or Openlayers. The issue was in the identifier for the utm32n-SRS. urn:ogc:def:crs:EPSG::25832 and EPSG:25832 aren't the same (the identifier, the SRS is)!

After replacing the short code with the long one (as the WFS-Server requires...) all the data has been loaded into Openlayers. Though I had to use ol.format.WFS().