Powershell WebRequest for DevOps API to retrieve Work Item doesn't include "Relations" in the response

I have a strange behavior when I perform a DevOps API request in Powershell to retrieve a Work Item with its relations. I found a bunch of other posts talking about this but I didn't find my scenario.

Some code to let you understand what I'm doing.

This is the wrapper around Invoke-WebRequest that I use for the API calls:

Function New-WebRequest {
    [CmdletBinding()]
    Param (

        [ValidateNotNullOrEmpty()]
        [ValidateSet("GET", "POST")]
        [string] $Method = "GET",

        [Parameter(Mandatory=$true)]
        [ValidateNotNullOrEmpty()]
        [string] $ApiCall,

        [ValidateNotNullOrEmpty()]
        [string] $RequestBody,

        [ValidateNotNullOrEmpty()]
        [string] $RequestContentType = "application/json"

    )

    if($ApiCall -notmatch $REGEX_URL) {
        Write-Error "The provided URL ($ApiCall) is not in the correct format"
        Exit 1
    }

    try
    {
        Write-Debug "API Request Call: [$ApiCall]"      

        $Command = "Invoke-WebRequest
            -Method $Method
            -Uri `"$ApiCall`"
            -UseBasicParsing
            -Headers @{Authorization = `"Basic $ENCODED_PAT`"}
            -ContentType $RequestContentType"
           
        if($PSBoundParameters.ContainsKey("RequestBody") -and -not([string]::IsNullOrWhiteSpace($RequestBody))) {
            Write-Debug "API Request Body: [$RequestBody]"
            $Command += " -Body '$RequestBody'"
        }

        $Exec = [ScriptBlock]::Create($Command -Replace "\r\n")
        $Response = & $Exec
        $StatusCode = $Response.StatusCode
    }
    catch {
        $StatusCode = $_.Exception.Response.StatusCode.value__
        Write-Error "Error Occured: $_"
    }

    if ($StatusCode -eq 200) {
        $ResponseBody = $Response.Content | ConvertFrom-Json
    } else {
        throw "API Call failed (Status code: $StatusCode)"
    }

    return $ResponseBody
}

This is the method I use to retrieve a work item:

Function Get-WorkItem {
    [CmdletBinding()]
    param (
        [Parameter(Mandatory=$true, Position=0)]
        [ValidateNotNullOrEmpty()]
        [ValidatePattern("\d{5,6}")]
        [string] $Id,

        [ValidateSet("All", "None", "Fields", "Links", "Relations")]
        [string] $Expand = "All",

        [string[]] $Fields,

        [switch] $IncludeUpdates
    )

    Write-Debug "Retrieving Work Item [$Id]..."
    $ApiCall = "$API_BASE_URL/wit/workitems/$($Id)?"

    $Params = @("`$expand=$Expand")
    if($PSBoundParameters.ContainsKey("Fields")) { 
        if($Expand -ne "None" -or $Expand -ne "Links" ) {
            Write-Error "The 'Fields' parameter can be used only if 'Expand' is 'None' or 'Links' as per API definition"
        } else {
            $Params += "fields=$($Fields -Join ",")"
        }
    }

    $ApiCall = Add-APIPart -URL $ApiCall -Params $Params

    $Body = New-WebRequest -ApiCall $ApiCall

    if($PSBoundParameters.ContainsKey("IncludeUpdates")) {
        $Call = "$API_BASE_URL/wit/workitems/$Id/updates"
        $Updates = (New-WebRequest -ApiCall $Call).Value
    }

    return (?: { $null -eq $Updates } `
        { $Body } `
        { @{
            Body = $Body;
            Updates = $Updates;
        } }
    )
}

As you can see, the "$expand" parameter is "All" by default (even if I tried also "Relations").

The issue is that when printing out the response in Powershell, I don't have the "Relations" field at all:

Name        MemberType   Definition
----        ----------   ----------
Equals      Method       bool Equals(System.Object obj)
GetHashCode Method       int GetHashCode()
GetType     Method       type GetType()
ToString    Method       string ToString()
fields      NoteProperty System.Management.Automation.PSCustomObject fields=@{System.AreaPath=....; System.TeamProject=....; System.IterationPath=....
id          NoteProperty int id=135215
rev         NoteProperty int rev=39
url         NoteProperty string url=https://dev.azure.com/nestle-globe/......./_apis/wit/workItems/135215
_links      NoteProperty System.Management.Automation.PSCustomObject _links=@{self=; workItemUpdates=; workItemRevisions=; workItemComments=; html=; workItemType=; fields=}

But if I open the link inside my browser I can see it:

response in browser

This is what I pass to the Web request:

DEBUG: Retrieving Work Item [135215]... DEBUG: API Request Call: [https://dev.azure.com/......./......../_apis/wit/workitems/135215?$expand=All&api-version=7.0]

I tried to pass different values to the "$expand" parameter of the REST API but it didn't make any difference. I also tried to remove the "-UseBasicParsing" switch in the Invoke-WebRequest but it didn't change anything.

From the response, it has API request call below:

https://dev.azure.com/......./......../_apis/wit/workitems/135215?$expand=All&api-version=7.0

Tried to put it directly in the Invoke-WebRequest method, it will report error as below:

The $ in $expand caused the error. Can use below format to fix:

1. use + to combine: $ApiCall = "https://dev.azure.com/{org}/{project}/_apis/wit/workitems/33223?$" + "expand=All&api-version=7.0"
2. or use %24 instead of $: $ApiCall = "https://dev.azure.com/wadez0770/wadetest1/_apis/wit/workitems/33223?%24expand=All&api-version=7.0"

In addition, for the Invoke-WebRequest response, you need to parse the json response:

$response = Invoke-WebRequest -Method GET -Uri $ApiCall -Headers $headers -ContentType $RequestContentType

# Parse the JSON response
$jsonResponse = $response.Content | ConvertFrom-Json

# Access the relations
$relations = $jsonResponse.relations

# Output the relations
$relations

Relations returned: