It seems like there is an issue with the TPMenuSystem v9.0.0 plugin in your Rust server. The error message indicates a NullReferenceException, which means that the plugin is trying to access an object that has not been initialized.
Specifically, the error occurs in the ButtonUI method of the TPMenuSystem plugin when it's trying to access an object instance that is currently null. This leads to a crash when the plugin tries to call the ChatMenu hook.
To resolve this issue, you may need to check the code of the TPMenuSystem plugin and ensure that all objects are properly initialized before accessing them. It's possible that a required object is not being set correctly, leading to the NullReferenceException.
Alternatively, you can reach out to the plugin developer or community support for assistance in troubleshooting and fixing this issue. They may be able to provide a patch or update to address the problem.