Long loading squid pages?

Question

Squid

Good afternoon, colleagues! There is squid v. 3.5.8, integration with AD is configured, all browsers are Chrome. Everything worked well, the following problem appeared the other day - when accessing some sites (for example, domestic search, you understand), the site is partially loaded and in the half-loaded version it hangs for about 5 minutes, and the browser reports "waiting for the creation of a tunnel by a proxy server." Everything is OK in the squid logs, as if it is working normally. Other sites work correctly. What I tried to do was disable the cache completely, disable IPv6. What else to pay attention to? If you turn off the proxy and go to the same site - it opens quickly and correctly. (total users about 12-15) Thank you!