Redux DevTools is causing RxJS's switchMap to behave differently. Why?

Question

I am working on an Angular 7 app, using NGRX store. I have installed Redux DevTools in my Chrome browser, so that I can make use of it during development.

I was more than puzzled when I noticed that a function was behaving differently, depending on whether Redux DevTools is enabled or disabled in the browser. In one case I was getting an error and in the other - everything was working fine.

The exact error was:

TypeError: You provided an invalid object where a stream was expected. 
You can provide an Observable, Promise, Array, or Iterable 

Luckily, I found the root of the problem in this answer - I had imported switchMap incorrectly due to WebStorm's auto import:

import { switchMap } from 'rxjs/internal/operators';

instead of

import { switchMap } from 'rxjs/operators';

However, I still can't understand what Redux DevTools has to do with it and why my code worked as if I was importing switchMap correctly when the tool was enabled, and the other way around - it was causing an error (as it generally should have been doing) when it was disabled.

I doubt that this code would be of much help here, but it is the one where the actual error occurred.

return this._http
            .post(url, body, { headers })
            .pipe(
                // This switch map and the throwError function were causing the error.
                switchMap((response: any) => {
                    // Please, do ignore the logic itself. There's a reason behind it.
                    const { data } = response;
                    return !!data ? of(data) : throwError('Invalid arguments');
                })
            );