Isssue Adding Web.Content Column to Web Data

First and most importantly: it looks like you're trying to connect to an API that requires OAuth2 authentication, and in order to do that you're going to need to create a custom connector as discussed here https://blog.crossjoin.co.uk/2021/08/29/connecting-to-rest-apis-with-oauth2-authentication-in-power-query-power-bi/ Even if you get past this particular issue, you might well run into other issues later on you can't work around. I suspect that building a custom connector might also help with this issue too.

For this specific error, this section on partitions in a presentation on data privacy that I gave a few years ago will explain the cause: https://youtu.be/RbqCA6srkmM?t=2002 (you'll probably want to watch the whole presentation for context though). Your response step is indeed accessing a data source and accessing data from other partitions so generating the string used for RelativePath and the record used for Headers in separate steps might help. You can also try setting the Skip Test Connection option on the data source in the Service (see https://blog.crossjoin.co.uk/2019/04/25/skip-test-connection-power-bi-refresh-failures/) as well. 

Chris