Authentication issues when calling multiple REST APIs with dynamic access token

Hi all, 

I am currently trying to call mutliple tables from an API provider in an Oauth authentication flow with a bearer token. The calls work fine individually but as soon as I want to call more than one table in Power Query Editor I get notified about authentication issues

I retrieve the token dynamically with the function fnGetToken. 

() =>
let

   //Send a POST request to login and get token
   loginData = "{""client_id"": """ & xxxxxxxxxxx & """, ""client_secret"": """ & xxxxxxxx & "}",
   loginHeaders = [
      #"Content-Type" = "application/json",
      #"accept" = "application/json", 
      #"login_id" = "xxxxxxxxx"
   ],

   loginResponse = Json.Document(Web.Contents(
      base_url, 
      [
      RelativePath = "v1/authenticate",
      Headers = loginHeaders,
      Content = Text.ToBinary(loginData)]
   )),
   data = loginResponse[data],
   token = "Bearer " & data[token]
in
   token

I have tried to call the fnGetToken function before the call and load the value on a variable as well as in the request itself. 

I have also used the Function.InvokeFunction with a 15 seconds delay using the #duration Parameter.

let
   accesstoken = fnGetToken(),
   getData = 
      Json.Document(
         Web.Contents(
            xxxxxbase_urlxxxxxx, 
            [
               RelativePath = xxxxxrelative_urlxxxxxx,
               Headers=[
                  #"login_id"="xxxxxxxxxx", 
                  accept="application/json", 
                  #"authorization" = accesstoken
               ]
            ]
         )
      ),
   data = getData[data]
in 
   data

My last approach would be to put each of them in individual Dataflows but would love to hear if there is a proper way with M code directly. Very much appreciate your help 🙂