Correct me if I am wrong but I think this is a visual bug. The IRST on the J35XS and possibly other aircraft with IRST get these weird green lines that cover the screen when you lock a target. I realized this started happening after the new major update.
Same bug on all my IRST jets. The IRST also no longer works like it used to, it will not maintain lock after you fire a missile. It immediately cuts lock and follows the missile instead. Didn’t used to do that last time I played…