Error while updating a Contact attribute over rest call (SFMC)

I have a script that updates the MPD (MobilePush Demographics Attribute) on the AllContacts List. I do this with a PATCH call to the contacts endpoint (https://developer.salesforce.com/docs/marketing/marketing-cloud/guide/updateContacts.html).

This works without a problem if the MPD Attribute is empty on the Contact. However, if I try to update the existing MPD Attribute I recieve this error:

{
"operationStatus": "FAIL",
"rowsAffected": 0,
"contactTypeID": 0,
"requestServiceMessageID": "8f0a0e6b-ee59-47f8-87ca-7219c713b603",
"responseDateTime": "2021-12-15T02:59:41.2904604-06:00",
"hasErrors": true,
"resultMessages": [
    {
        "resultType": "Validation",
        "resultClass": "Error",
        "resultCode": "InvalidAttributeSet",
        "message": "The Attribute Set [MobilePush Demographics] has validation errors.",
        "innerResultMessages": [
            {
                "resultType": "Validation",
                "resultClass": "Error",
                "resultCode": "InvalidInnerValueAttribute",
                "message": "[DefinitionKey: CreatedDate], [DefinitionName: Created Date], [DefinitionID: da41f36f-9d16-ea11-b82d-b88303587ab1] :: The Attribute has an 'Inner Value' that could not be parsed to the correct data type. [DefinitionName: Created Date], [DefinitionID: da41f36f-9d16-ea11-b82d-b88303587ab1]",
                "innerResultMessages": [
                    {
                        "resultType": "Validation",
                        "resultClass": "Error",
                        "resultCode": "InvalidDate",
                        "message": ""
                    }
                ]
            },
            {
                "resultType": "Validation",
                "resultClass": "Error",
                "resultCode": "InvalidInnerValueAttribute",
                "message": "[DefinitionKey: ModifiedDate], [DefinitionName: Modified Date], [DefinitionID: e441f36f-9d16-ea11-b82d-b88303587ab1] :: The Attribute has an 'Inner Value' that could not be parsed to the correct data type. [DefinitionName: Modified Date], [DefinitionID: e441f36f-9d16-ea11-b82d-b88303587ab1]",
                "innerResultMessages": [
                    {
                        "resultType": "Validation",
                        "resultClass": "Error",
                        "resultCode": "InvalidDate",
                        "message": ""
                    }
                ]
            }
        ]
    },
    {
        "resultType": "Operational",
        "resultClass": "Error",
        "resultCode": "Update Failed",
        "message": "Update failed for one or more AttributeSets. Note: Updates aren't allowed on attributes that form the primary Key of the attributeset"
    }
],
"serviceMessageID": "7d4272a7-8396-4d35-b699-1d62faa58a03"
}

This is the Payload that I sent in the PATCH rest call (wich works for creating the MPD Attribute):

{
"contactKey": "0030E000014AJw7QAG",
"attributeSets": [
    {
        "name": "MobilePush Demographics",
        "items": [
            {
                "values": [
                    {
                        "name": "Application",
                        "value": "60fea8bf-1f51-44d0-8d27-3fb9aexxxxxx"
                    },
                    {
                        "name": "Device ID",
                        "value": "E94A5018D2D10A3EBFE4E71FBE9D4010C5AAF90123E02E80289380F91Dxxxxxx"
                    },
                    {
                        "name": "System Token",
                        "value": "cfGsADOSRveQGsT-j3GWfr:APA91bGxe4a5oKlbBLLF7jz3xcK5pqdU_-95OPCrEQiNv92LYJZBHskHjlX6gpIKxio6JqCfKvcQ2uoZF435bxf5qrR0kJqTsL_mXJUmTniRmaJ0WSlMLclvxwx2aW7Gtaa7qBxxxxxx"
                    },
                    {
                        "name": "Platform",
                        "value": "Android OS"
                    }
                ]
            }
        ]
    }
]}

Does anybody know why I receive this error message? Thank you in advance!