Scrapy twisted.python.failure.Failure twisted.internet.error.ConnectionLost: Connection to the other side was lost in a non-clean fashion. How to decide?

Question

Python

Today the site parser started giving this error instead of collecting information:

[scrapy.downloadermiddlewares.retry] DEBUG: Retrying <GET https://site.com> (failed 1 times): [<twisted.python.failure.Failure twisted.internet.error.ConnectionLost: Connection lost.>]

Turned on Psiphon - does not help. Disabling/changing the Telnet port does not work. What is the problem and how can it be solved?