If you add a message setting such as message_hello, the NPC will be deleted.
Also, they will become hostile towards the patrol helicopter.
Please fix this.

Fix what? How are you adding the message_hello? With the command or editing the datafile wrong?
i Think its just you. Please fix.

What are you supposed to set for message_hello?
If you set a message, the NPC that was already set will be deleted
and the console will output "NPCxx deleted."
The same thing happened if I deleted other plugins and only left the plugin-related stuff, and the same symptoms occurred on multiple servers.

Merged post

Also, you said that this is just my problem,
but other people have reported that NPCs are treating them with hostility as well.
I would like you to tell me the solution (I know this can be implemented with other plugins, but I want to solve this problem with just this plugin) and include it in the description.

You still did not show and tell me how you are setting the message. And as for hostility that has been answered many times and im not going to answer every one that posts the problem with out reading first.