Fix JS client not sending requests to a server

We have a Frontend and a Backend in our app. There is a JS code generated every time using a template - with custom variables and conditions. Hot it all works: 1. When a visitor has reached the site, the backend records user as a new visitor with the status "Got Script" . It also detects the ability to redirect a user to another URL1 (Tracker request) and outputs result - compiled JS code. 2. Visitor on the website is redirected after some time (about 1 second) to a Tracker URL1. 3. On the Tracker request, the visitor goes to the new URL2 returned by the Tracker (service for redirection detecting and control), -> searches for the URL to redirect the Visitor to (depending on it's data, such as IP or device parameters), updates the Visitor status to "Redirected To Link", responds with HTTP-redirect (status 302). The problem: Some part of Visitors is not redirected to the Tracker, although it should have been with probability about 98%. But in fact, it is about 90%. We are asking to fix the problem at the frontend - why not every user is being redirected.