Incorrect dns work after site transfer, what should I do?

Question

Domain Name System

Background: there was a project (for simplicity, site.com) on hosting (fornex), domain on reg.ru; I had to transfer the site to my server.
NS records on reg ru rewrote to new ones (own dns). Waited for update. But when I go to the main site.com, for some reason I get to the old hosting instead of my server, the site has already been deleted on that hosting, it naturally redirects to 404, but here is the juice: when a redirect to 404 occurs, I get to NEW server. As a result, on the new server, everything except the main one works correctly. As if when entering the main url for the server, one ns is registered, for the rest - others.
I think it has something to do with the cache of the provider or the cache of the device itself.On devices that have never visited this site before, everything works properly.
There are a lot of other sites on their dns, everything works as it should. New ns entries are displayed on 2ip and mxtools (everything is OK)

Answer 1

nslookup and other dns diagnostics will help you. You need to see what kind of records were there, what ttl they had

Answer 2

Most likely the hoster is an asshole and gave 404-ku through the 301st redirect (it is cached).
Try to enter the porn mode of the browser.