First off thanks for supporting me in getting all my heavy plugins. Sorry you are having issues with this one..
Heavy Military tunnel uses the exact same logic for turret targeting as heavy oil rig. If heavy oil rig is working fine for you, that leads me further to believe you have another plugin that is conflicting in some way. Certain plugins only work in certain zones/areas just like the heavy plugins so just because other heavy plugins work in different locations, that doesn't rule out a plugin conflict.
I'd like to help you but I'm still unable to recreate the issue on my server and you haven't given me a ton to go off of other than it works elsewhere. Are you able to setup a test server/environment where you can run just the heavy military tunnel plugin and confirm it works for you? Then you can introduce other plugins and see if you can pinpoint when it starts happening? Thanks!