Admins can't use /stop

I recently setup my vanilla server to automatically restart when someone uses /stop. It works fine in the terminal, but when an admin tries to use it in game, it says something to the extent of "Insufficient permissions". I set the op-permission-level to 4, but it wont work. I'm wondering if the auto-restart is affecting something.

Here is my start.command:

#!/bin/bash
cd "$(dirname "$0")"
while true
do
java -Xmx1G -Xms1G -jar minecraft_server.jar
sleep 1
done