ntozier Thanks for your reply. I have updated the Osticket version to v1.15.3.1(FYI Mysql Version is 10.3.17 and Php Version 7.3.20.) and checked all the things :
Network speed is around 40mbps.
Ram(16GB for Application server and 32GB for DB Server) and CPU(4cores for application and 8cores for DB) utilization is very less, attaching the screenshot.
Database storage engine is InnoDB only.
Still the issue is same, while opening every ticket /jquery-3.5.1.min.js?65ca4e6 this JS file is getting canceled after every 30 seconds, it will start again and then it will open after 15 seconds, can you tell why is this happening ? this one is taking time, attaching the screenshot.