Where there is extra space when you paste in html page code?

Hi all.

Such a situation: write a module for Bitrix(similar to a plugin on wordpress) and was faced with a strange situation

a screenshot of the source code on wordpress: joxi.ru/VrwM1nxsOeoQv2
the arrow shows where is the problem.

a screenshot of the source code on Bitriks: joxi.ru/EA46E1YfwEXzMm
and there was a gap...why????

this html code is generated on the server, loaded via ajax and inserted into the page and everything.
But for some reason on wordpress it is normal inserts and that Bitrix adds such a gap...

Anybody know how it turns out?

Code is generated on the server with no spaces, blank appears after the $("#container").html(ajax.html) in Bitrix
joxi.ru/82QqyMXTjx8Jq2

Thank you!