Windows 10, Emacs 26.1
Here steps of reproduce:

1. Start emacs -Q
2. Input some text (see step1.jpg)
3. M-x isearch-toggle-case-fold   (see step2.jpg)
4. C-s (isearch) HELLO  (see step3.jpg)
5. C-g
6. M-x isearch-toggle-case-fold
7. and see result on step4.jpg








-----Original Message-----
From: Eli Zaretskii <eliz@gnu.org> 
Sent: Wednesday, July 31, 2019 17:56
To: Noam Postavsky <npostavs@gmail.com>
Cc: a_subscriber@mail.ru; 36871@debbugs.gnu.org
Subject: Re: bug#36871: 26.1; I-search-toggle-csse-fold

> From: Noam Postavsky <npostavs@gmail.com>
> Cc: "a_subscriber" <a_subscriber@mail.ru>,  36871@debbugs.gnu.org
> Date: Wed, 31 Jul 2019 10:11:37 -0400
> 
> I'm assuming step 2 should read M-x isearch-toggle-case-fold.

Yes, that's what I did as well.

Thanks for testing the recipe.