Possible Bug: Missing IPTC data after uploading via Siri Shortcuts

Hello all,

I am trying to automate the upload to WordPress via Siri Shortcuts on my iPad. What I found out:

There are one entry containing the caption of a photo with the identifier: 2#120.
In one scenario this data is available in WordPress after upload and in two scenarios not:

Working scenario:
If I use the WordPress app and upload the photo out of my photos app it is working and in wordpress this data are avalaible:

1#090 = %G
2#000 = ?
2#080 = PICTOR PHOTOGRAPHY
2#062 = 20200204
2#063 = 213203
2#005 = Apple Smart Keyboard Folio für das iPad Pro
2#120 = Das Smart Keyboard Folio von Apple ist eine vollwertige Tastatur, das nur mit Magneten als Halterung auskommt. Somit erspart man sich ein aufdringliches Case und der schlanke Formfaktor vom iPad Pro kommt weiterhin voll zu Geltung.
2#060 = 213203
2#116 = (c) by PICTOR PHOTOGRAPHY
2#055 = 20200204

1st not working scenario
If I am uploading the same image via the media uploaded in WordPress the entry 2#120 is missing:

1#090 = %G
2#000 = ?
2#005 = Apple Smart Keyboard Folio für das iPad Pro
2#055 = 20200204
2#060 = 213203
2#062 = 20200204
2#063 = 213203
2#080 = PICTOR PHOTOGRAPHY
2#116 = (c) by PICTOR PHOTOGRAPHY

2nd not working scenario
Upload via Siri shortcut produces the same data as in the scenario before. In this Shortcut I am select one photo in the photo app, call the share sheet and use the provided WordPress shortcut:

1#090 = %G
2#000 = ?
2#005 = Apple Smart Keyboard Folio für das iPad Pro
2#055 = 20200204
2#060 = 213203
2#062 = 20200204
2#063 = 213203
2#080 = PICTOR PHOTOGRAPHY
2#116 = (c) by PICTOR PHOTOGRAPHY

The photos raw meta data are this:

"{IPTC}": {
    Byline =     (
        "PICTOR PHOTOGRAPHY"
    );
    "Caption/Abstract" = "Das Smart Keyboard Folio von Apple ist eine vollwertige Tastatur,
das nur mit Magneten als Halterung auskommt. Somit erspart man sich ein aufdringliches Case und der schlanke Formfaktor vom iPad Pro kommt weiterhin voll zu Geltung.";
    CopyrightNotice = "(c) by PICTOR PHOTOGRAPHY";
    DateCreated = 20200204;
    DigitalCreationDate = 20200204;
    DigitalCreationTime = 213203;
    ObjectName = "Apple Smart Keyboard Folio f\U00fcr das iPad Pro";
    TimeCreated = 213203;
},
"DPIWidth": 300,
"Depth": 8,
"PixelWidth": 2400,
"{Exif}": {
    ApertureValue = "6.33985";
    BrightnessValue = "5.41171875";
    ColorSpace = 1;
    Contrast = 0;
    DateTimeDigitized = "2020:02:04 21:32:03";
    DateTimeOriginal = "2020:02:04 21:32:03";
    DigitalZoomRatio = 1;
    ExifVersion =     (
        2,
        3,
        1
    );
    ExposureBiasValue = 0;
    ExposureMode = 1;
    ExposureProgram = 1;
    ExposureTime = "0.1";
    FNumber = 9;
    FileSource = 3;
    Flash = 16;
    FocalLenIn35mmFilm = 45;
    FocalLength = 30;
    ISOSpeedRatings =     (
        100
    );
    LensModel = "E 28-75mm F2.8-2.8";
    LightSource = 255;
    MaxApertureValue = "2.970853658536585";
    MeteringMode = 5;
    OffsetTime = "+02:00";
    RecommendedExposureIndex = 100;
    Saturation = 0;
    SceneCaptureType = 0;
    SceneType = 1;
    SensitivityType = 2;
    Sharpness = 0;
    ShutterSpeedValue = "3.321928";
    WhiteBalance = 1;
},
"{ExifAux}": {
    LensModel = "E 28-75mm F2.8-2.8";
},
"ColorModel": RGB,
"ProfileName": sRGB IEC61966-2.1,
"{TIFF}": {
    Artist = "PICTOR PHOTOGRAPHY";
    Copyright = "(c) by PICTOR PHOTOGRAPHY";
    DateTime = "2020:06:01 16:08:08";
    ImageDescription = "Das Smart Keyboard Folio von Apple ist eine vollwertige Tastatur,
das nur mit Magneten als Halterung auskommt. Somit erspart man sich ein aufdringliches Case und der schlanke Formfaktor vom iPad Pro kommt weiterhin voll zu Geltung.";
    Make = SONY;
    Model = "ILCE-6500";
    ResolutionUnit = 2;
    Software = "ILCE-6500 v1.06";
    XResolution = 300;
    YResolution = 300;
},
"PixelHeight": 1350,
"DPIHeight": 300

I don’t know how the behavior is so different and don’t know where the data are getting lost. Perhaps anyone can support me.

Thanks in advance
Thorsten