Why does the output from a third-party script appear in the admin panel while scripts are running?

Question

PHP

Hello.
There is a site on Bitrix, recently I began to notice strange things, while some scripts are running in the site admin panel, such as sending a newsletter or executing code in the php command line in the admin panel, the execution of the current script stops and the following output appears:
{"status" :"error","text":"Data already sent."}
This json response returns a completely third-party script that processes requests in the public part of the site, and where does this json response come from in the admin panel during the execution of unrelated code?
I suspect that this is somehow related to the cache, I meet this for the first time and ask knowledgeable people - tell me what it could be, where to look to find the cause.
PS This glitch does not appear constantly, but from time to time and appears in various parts of the admin panel.

Answer 1

hooks/events and of course a crooked third-party script are the most likely sources of the "problem". And how do you imagine a concrete answer to such an abstract question?