Explorer successfully executes queries but won't load the schema

**Intended outcome:**

When I visit the explorer I should have an up to date schema from the API. I see errors when loading a query from the "Queries" tab however the query executes at my endpoint successful.

**Actual outcome:**

I have the default schema (id, __typename) - there is no way that I can reload the schema.

**How to reproduce the issue:**

My endpoint is at `localhost:4200/api/graphql`. I have a custom httpLink and webSocket link, however I have also set the URI to `localhost:4200/api/graphql` and connectToDevTools: true - Authentication is not required to load the schema, and I'm able to successfully load it from apollo playground (at localhost:4200/api/graphql) when not authenticated.

**Desktop (please complete the following information):**
- OS: Ubuntu 20
- Browser [e.g. chrome, safari]: Brave
- Browser version [e.g. 22]: [Version 1.41.100 Chromium: 103.0.5060.134 (Official Build) (64-bit)](https://brave.com/latest/)
- Extension version [e.g. 3.0] 4.1.2

Start by reproducing the Explorer schema-loading failure against the reported localhost:4200/api/graphql endpoint, including the Queries tab and the custom HTTP and WebSocket links. Trace the Explorer's schema-loading path and compare it with the successful Apollo Playground request; done means the Explorer shows the current API schema and queries load without errors.

Written by the indexing model from the issue text.