I have to use modsec with nginx (nginx version 1.16.1) However, it takes about 2 weeks for us to run out of memory, the system did not self-release the ram. How can I fix it?

Whenever any rule is triggered , modsec shows 500 internal server error, instead of 403 access denied. nginx version: nginx/1.16.0 (OptimEngine) built by gcc 6.3.0 20170516 (Debian 6.3.0-18+deb9u1) ...