Strange redirect, not an application, not a web server. Redirect on the web?

Question

PHP

I decided to transfer the project to another hosting, and found a strange redirect, when you go to a certain page, there is always a redirect to another page. Always from one specific page, to another specific page, conditionally from /sample-page to /sample-page/all.
What we have:
1) This is not in the logic of the application (website), since I immediately put die on the entry point and the redirect always works
2) This is not at the level of the web server, since I didn’t find anything like that in the nginx config, but I didn’t find it in the access logs I see no redirect, as if the request immediately goes to /sample-page/all.
3) This is not a browser or operating system cache (it seems like this happens), I checked it using another browser and from another device
4) I make a request via postman and I see that when requested, /sample-page returns http301 to /sample-page/all

Total, wtf?

I'm writing to the hoster, maybe he will tell you, the answer is - everything is OK with us, there is no redirect. I turn off wifi on my phone and try to log in with 4G, there is NO redirect!

That is, somehow, it is in my wifi network that such a redirect occurs.
What is it and how to deal with it?