I'm happy you removed the car protection plugin, it didn't even protect your car. But with the "new" way of placing a sign and claiming it yours is... a bit stupid to be honest. Anyone with enough metal can just place a sign on a car and leave it be, just need to watch a new player get in and report him. I don't like getting my car blown up but really, it's your own job to keep it "safe".
The metal signs were how the servers operated before the car plugin. We didn't make the plugin so we can't fix the bugs in it. We went back to the old method of claiming cars because it was pretty reliable. If the name of the person driving doesn't match the sign... We ban. The plugin did nothing to prevent cars from being blown up. A metal sign will take a number of hits before it breaks.