Find an error in the code page of the site in Tilda

Task:
Find the error in the code. The result of the work is a working code with a feedback form and a correct pop-up form with a "send" button. We have several pages with this code and error. We need to fix it on one page and tell us what the reason was so that we can fix the error on the others on our own.

Description of the problem:
On the page of our site in Tilda there is a block T123 with custom html code.
The function of the code is to hide the building block with the application form, so that instead of it the application block is also displayed, but made in zero block for the overall design of the site.
This code contains an error that affects a completely different block BF502N (pop-up form) with which it has nothing to do with it. Because of this code, the "send" button is not displayed in the BF502N block.

Code examples, errors and a link for clarity will be sent to the customer