thanks @Cold-Egg . i tried with php8.3 but for some reason, I started seeing so many email failures. my email provider is godaddy. due to that I reverted back to 81 and now everything is running smooth again. may be other packages or plugins have issue. don't know and haven't debugged. for now can't do this on a live website as well. so best option was to revert back. will test on the test website later but in meanwhile if someone else also facing similar issues, and has found a solution to the problem then please do let me know.
