Upgrade to Laraval 9 got issues

Hello there,

I am new to the forum and was stuck with an issue where we upgraded Laraval framework from version 5.8 to 9. Our application servers are hosted into aws under application load balancer.so we have two set of app stack is running. one is app with Laravel 9 (L9) and another is with Laravel 5(L5) . the L5 servers are running with no issues. where our L9 servers are getting timedout and loadbalancer shows unhealthy and the server cpu usage goes to 100% constantly. Please refer this doc from github https://github.com/jameslee007/Laraval9_issue/blob/main/L9%20issue.docx.

So far we don't know why the process D in php-fpm and why the cpu goes high. Please help.